A text-book of clinical diagnosis by laboratory methods: for the use of students, practitioners, and laboratory workers

Front matter

p

Qass.

Book

Preface

This book has emanated from a desire to satisfy the demands made by my pupils, and it has been prepared to meet the present needs of the student and of the general practitioner.

It is hoped that the volume may prove of practical value, although it does not attempt to furnish more than a working introduction to the department of medicine under discussion. It is, however, designed as a practical guide, and the methods described are such as can be carried out with a minimum of complicated apparatus.

Special attention has been given to outlining in progressive steps the various procedures in clinical technic, such steps being illustrated whenever possible. Besides the detailed descriptions of methods of examination, the diagnostic significance of the chnical findings is given under special headings and is frequently accompanied by tables of differentiation.

In the chapter on the blood the more recent methods for examination and staining are described and illustrated by original drawings; and the subject of Serum-diagnosis is carefully considered. The protozoan parasites known to invade the blood of the lower animals are described in connection with the malarial parasite.

In the chapter on the urine the newer methods for the estimation of sugar, Bence-Jones' albumin, uric acid, and purin have received consideration, and the whole chapter is illustrated by a large number of original half-tones and colored plates.

An unusual amount of space is given to the consideration of Animal Parasites, Diseases of the Skin, Transudates and Exudates, and the Secretions of the Eye and Ear. Inoscopy and Cytodiagnosis have been briefly considered.

I am indebted to Dr. Chas. Wardell Stiles for valuable suggestions regarding the subject of animal parasites; to Dr. John A. McKenna, who read the proof, and to W. B. Saunders & Co. for special courtesies rendered while the book was in press. In material taken from the literature I have endeavored to give credit in each instance.

Philadelphia, Aicgust, 1904.

Introduction

PAGE

The Diaphragm, 17; Light, 18; ObHque Light, 18; the Getting of Light with the Mirror, 19; Focus, 22; Working Distance, "22; the Condenser, 25; Care of the Microscope, 25; Measuring of Specimens, 26; Ringing of Specimens, 28.

THE BLOOD.

Tests for the Recognition of Blood 31

Teichmann's Test, 31; Guaiacum Test, 31.

Estimation of the Total Volume of the Blood 31

Haldane and Smith Method, 31.

Study of the Fresh Blood 32

Preparation of Shdes and Cover-glasses, 32: Chnical Blood Reports, ^^. Collection of Blood, 2>3- Immediate Examination of Blood and Making of Smears, 34: Immediate Examination, 34; Smears, 35; Life of the Blood-cells, ^y. Microscopic Study of Fresh Blood, 37. Estimation of the Volume of the Red Cells and the Plasma, 38; Hematocrit, 38. Estimation of the Specific Gravity, 40: Hammerschlag's Method, 40; Wright's Coagulometer, 41. Hemoglobin, 41: Oxyhemoglobin, 42; Reduced Hemoglobin, 42; Hemoglobinemia, 42; Methemoglobin, 42; Carbonic-oxid Hemoglobin, 43; Hematin, 43; Hematoidin, 43; Hemosiderin, 43; Melanin, 43; Spectroscopic Examination of the Blood, 43; Corroborative Tests, 45; Dare's Hemoglobinometer, 46; Oliver's Hemoglobinometer, 47; Von Fleischl's Hemoglobinometer, 48; Tallquist's Hemoglobin Scale, 51. Counting of the Blood-corpuscles, 52: Method of Thoma-Zeiss, 52; OKver's Hemocytometer, 58. Alkahnity of the Blood, 60. Acidity of the Blood, 64. Composition of the Whole Blood, 64: Albumins, 64; Peptone, 64; Inorganic Substances of the Blood, 65; Urea, 65; Uric Acid, 65; Glycogen, 65; Fat (Lipemia) and Fatty Acids, 66; Glucose, 67; Diabetic Blood, 68; Acetonemia, 6g; Cholemia, 6g; Biliary Acids in the Serum, 69; Globulicidal Properties of Serum, 70; Diastatic Ferment of Blood, 70. Cryoscopy of the Blood, 70. Omostic Properties of the Blood, 73: Normal Salt Solution, 73.

Study of Fixed and Stained Blood 74

Slides and Cover-glasses, 74. Staining, 76: Eosin and Hematoxylin, 76. Microscopic Examination of the Stained Blood, 77: Normal Blood, 77; Fixing and Staining Combined, 77; Wright's Method, 78; Ehrlich's Tricolor Mixture, 79. The Erythrocytes, 81. Anemia, 82; Chemistry of the Erythrocytes, 82. Hydremia, 83. Anhydremia, 83. Polycythemia, 84: Cyanosis, 84; Burns, 85; Anesthesia, 85; Effect of Altitude upon the Blood, 86; Polycythemia of Poisons, 88. Secondary Anemia, 88: Viscosity, 88; Endoglobular Changes (Simple Decoloration), 89; Changes in Shape, Size, and Motihty, 89; Atypical Staining Properties, 90; Granular Basophilia, 91; Necrosis, 92; Megaloblasts, 92; Normoblast, 93; Microblast, 94; Oligemia (Quantitative Anemia), 94;

lO CONTENTS.

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Mclanemia, 94. Normal Leukocytes, 94: Lymphocytes, 95; Large Mononuclears, 95; Polynuclear Forms, 96; Mast Cell, 96; Eosinophil, 96. Leukocytes in Disease, 96; Myelocytes, 97; Transitional Neutrophils, 9S; Turck's Stimulating Form, 98; Degenerated Leukocytes, 98. Differential Counting of the Leukocytes, 98. Blood-plates, 100. Blood Dust, 100. Leukocytosis, loi: Toxic Leukocytosis, 102; Leukocytosis of Malignancy, 102; Leukocytosis of Anesthesia, 102; Drugs, 103; Leukopenia (Hypoleukocytosis), 104; Lymphocytosis, 104; Eosinophilia, 105; Diminution of the Eosinophils (Hypoeosinophiha), 107.

Bacteriology of the Blood 107

The Reaction of Bacteria of the Blood, and their Products, 108. Method of Collecting Blood, 109: Films, no; Staining, no; Animal Inoculation, no. Bacteria of the Blood, in: Anthrax, in; Relapsing Fever, in; Tubercle Bacillus, 112; Leprosy, 112; Typhoid Fever, n 2 ; Suppuration, 113; Pneumonia, 113; Influenza, 113; Epidemic Meningitis, 114; Purpura, 114; Ulcerative Endocarditis, 114; Gonococcus, 114; Plague, 114; Diphtheria, 114; Fungi, 114; Malta Fever, 114; Chorea, 115; Scarlet Fever, 115; Scurvy, 115; Leukemia, 115. Invasion of the Red Bone-marrow by Bacteria, 115: Typhoid Fever, 116; Tuberculosis, 116; Diphtheria, 116; Scarlet Fever, 116; Erysipelas, 116. Serum-Diagnosis, 116: Streptocolysis, 117. Widal Reaction, 118: Paratyphoid Fever, 124; Dysentery, 124; Plague, 124; Cholera, 124; Tuberculosis, 125; Malta Fever, 125; Glanders, 125; Pneumonia, 125; Bacillus Pyocyaneus, 125; Fungi, 125.

Special Pathology of the Blood 126

Pernicious Anemia, 126. Chlorosis, 127. Leukemia, 129: Myeloid Leukemia, 130; Lymphatic Leukemia, 131. Pseudoleukemia (Hodgkin's Disease), 132. Splenic Anemia, 132. Acute Infectious Diseases, 133: Pneumonia, 133; Typhoid Fever, 133; Diphtheria, 135; Scarlet Fever, 135; Measles, 136; Small-pox, 136; Vaccinia, 137; Suppuration, 137; Appendicitis, 137; Erysipelas, 138; Acute Rheumatism, 138; Whooping-cough, 138; Tonsillitis and Serous Effusions, 138; Influenza, 138; Bubonic Plague, 139; Alalta Fever, 139; Yellow Fever, 139; Gonorrhea, 139; Actinomycosis, 139; Anthrax and Glanders, 139; Leprosy, 140; Bacilli, 140; Takosis, 140; Hemocytolysis, 141; Purpura Hemorrhagica, 141; Scurvy, 142; Hemophilia, 142; Addison's Disease, 142; Myxedema, 142.

Parasitic Diseases Affecting the Blood 143

Uncinaria Duodenale (Ankylostoma Duodenale), 143. Strongyloides Intestinalis, 143. Ascaris Lumbricoides, Oxyuris Vermicularis, Trichocephalus Dispar, 143. Trichinosis, 146. Schistosoma (Distoma, Bilharzia) Haematobium, 147. Dibothriocephalus Latus, Taenia Solium and Taenia Mediocanellata, 147. Filariasis, 147. Dracunculus Medinensis (Guinea- worm), 149. Trypanosomiasis, 151: the Parasite, 151; Sleeping Sickness, 153; Animals, 153. Malaria, 153: Zoologic Affinities, 153; the Malarial Parasite, 157; Method of Examination, 157; Staining, 158; Hyaline Bodies, 159; Pigmented Bodies, 159; Segmenting Bodies, 160; Crescentic Bodies, 162; Oval Bodies, 162; Extracellular Bodies, 162; Flagella, 162.

THE URINE.

Physical Properties of the Urine 168

Naked-eye Appearance, 168: Quantity, 168; Color, 169; Transparency, 171; Odor, 172; Consistence, 172. Specific Gravity, 172: Increase, 172; Decrease, 172; Solids of the Urine, 174. Electric Conductivity of the Urine, 175. Reaction of the Urine, 176: Decreased Acidity, 176; Increased Acidity, 176; Alkaline Reaction, 176; Amphoteric Reaction, 177; Fixed and Volatile Alkalis, i77-

CONTENTS. II

PAGE

Chemistry of the Urixe 177

Mineral Ash, 178. Chlorids, 179. Phosphates, 181: Earthy Phosphates, 182; Alkaline Phosphates, 182; Estimation of Phosphoric Acid, 184. Sulphates, 185: Ethereal Sulphates, 187; Neutral Sulphur, 187; Loosely Combined Sulphur in Urine, 187. Centrifugal Analysis, 189: Estimation of Chlorids, 189; Estimation of Phosphates, 190; Estimation of Sulphates, 191 Urea, 192: Estimation of Total Nitrogen, 195. Uric Acid, 196. Xanthin Bases, 200. Hippuric Acid, 201. Oxalic Acid, 203: Oxalic-acid Diathesis, 203; Quantitative Estimation of Oxalic Acid, 204. Kreatin and Kreatinin, 204: Weyl's Test, 205. Proteids in the Urine, 205: Mucin, 205; Serum-albumin and Serum-globulin in the Urine, 206: Separation of Albumin and Globulin, 206; Douglas' Method, 206; Author's Method, 207; Serum-globulin, 214; Mucin (Nucleo-albumin), 215; Emulsion-albuminuria, 216; Albumoses, 216; Peptones, 217; Bence- Jones' Albumose, 218; Hematuria, 221; Hemoglobinuria, 222; Methemoglobinuria, 223; Hematoporphyrinuria, 223; Histon, 223; Fibrin, 224. Carbohydrates (Sugar) in Urine, 225: Glucose, 224; Tests for Glucosuria, 226; Optical Saccharimetry, 236; Lactose, 238; Pentoses, 238; Bail's Test, 238; Tollen's Phoroglucin Test, 239. Bile in the Urine, 239. Acetone, 240: Tests for Aceto-acetic Acid, 240; Tests for Acetone, 241. Oxybutyric Acid, 242. Diacetic Acid, 243: Gerhardt's Test, 243; Arnold's Test, 243. Lactic Acid, 244. Cholesterin, 245. Ammonia in the Urine, 246. Cystin, 246. Pyuria, 246. Alkaptonuria, 247. Urein, 248. Ehrlich Diazo-reaction, 249. Ehrlich Dimethylamidobenzaldehyd Reaction, 249. The Volatile Fatty Acids, 250. Fat, 251. Chyluria, 252. Ptomains, 254. Gases, 254. Effect of Drugs upon the Urine, 255.

Microscopic Study of the Urine 257

Sedimentation, 257. Microscopic Technic, 258: Light, 258; Focus, 258; Permanent INIounts, 258; Washing Sediments, 259; Casts, 259. Urinary Sediments, 260: Inorganic Sediments, 260; Uric Acid, 264; Calcium Oxalate, 265; Calcium Sulphate, 266; Calcium and Magnesium Soaps, 266; Neutral Calcium Phosphates, 267; Boric Acid, 267; Tyrosin and Leucin, 267; Bilirubin, 270; Hematoidin, 270; "Triple Phosphates, 271; Basic Phosphates of Magnesium, 271; Hippuric Acid, 271; Cystin, 271; Xanthin, 272; Cholesterin, 272; Acid Ammonium Urates, 272; Acid Urate of Sodium, 273; Amorphous Deposits, 274; Crystalhne Sediments from Alkaline Urine, 275; Amorphous Alkaline Deposits, 277. Organic Sediments, 278: Leukocytes, 278; Pus, 278; Epithelia, 279; Blood, 281. Casts (Tube-casts; Renal Casts), 283: Staining of Casts, 284; Urate Casts, 284; Hyaline Casts, 285; Granular Casts, 286; Blood-casts, 287; Epithelial Casts, 288; Pus-cells, 288; Fatty Acids, 289; Amyloid Casts, 289; Cylindroids, 290; Floaters, 291; Spermatozoa, 291; Fragments of Tumors, 291. Animal Parasites, 292: Tgenia Echinococcus, 292; Filaria Sanguinis Hominis, 294; Schistosoma Haematobium, 295; Oxyuris Vermicularis, 297; Ascaris Lumbricoides, 297; Rhabditis Genitalis, 297; Trichocephalus Dispar, 298; Anguillula Aceti, 298; Eustrongylus Gigas, 299; Bothriocephalus Liguloides, 300; Amoeba Urogenitalis, 300; Infusoria, 300. Vegetable Parasites, 300: Fungi, 300; Actinomyces, 301; Aspergillus, 301; Bacteriuria, 301.

GASTRIC CONTENTS.

Method of Collection, 308: the Stomach-tube, 308; Washing the Stomach, 313; Einhorn's Instrument, 314. Test-meal, 315: Ewald-Boas' Test-breakfast, 315; Riegel's Test-dinner, 316; Boas' Test-breakfast, 316; Salzer Test-meal, 316. Characteristic Features of the Gastric Juice, 317. Motor Power of the Stomach, 318: Leube's Method, 31S; Ewald-Sievers'

12 CONTENTS.

PAGE

Method, 318, Resorptivc Power of the Stomach, 319. Giinzburg's Method for Indirectly Examining the Gastric Juice, 319.

Chemistry of the Gastric Contents 320

Acidity, 321: Total Acidity, 323; Amount of Hydrochloric Acid, 324; Source and Significance of Hydrochloric Acid, 326; Tests for Free Hydrochloric Acid, 328. Ferments and their Zymogens, 335: Test for Pepsin and Pepsinogen, 336; Chymosin, 338. Products of Gastric Digestion, 340: Proteid Digestion, 340; Albuminoids, 341; Digestion of Carbohydrates, 341; Digestion of Fat, 342. Fatty Acids, 342: Test for Butyric Acid, 343; Test for Acetic Acid, 343; Estimation of Organic Acids, 343; Lactic Acid, 344. Acetone, 348. Gases, 349.

Microscopic Study of the Gastric Fluid 350

The Vomit 352

Odor, 352; Saliva, 353; Mucus, 353; Bile, 354; Stercoraceous Vomit, 354; Blood, 354; Pus, 355; Parasites, 355.

THE FECES.

Collection of the Feces, 356. General Characters of the Feces during Health and during Disease, 357: Constipation, 358; Amount, 358; Form, 359; Odor, 359; Color of Stools, 360.

Chemistry of the Feces 362

Reaction of the Stools, 362. Composition of the Feces, 363. Tyrosin, 365. Fatty Acids, 367: Physical Properties of Fatty Acids, 367 Biliary Acids, 368. Pigments of the Feces, 369. Cholesterin, 370.

Particles of Food, etc., 371; Mucoid, Serous, and Bloody Stools, 372; Epithelial Cells, 374; Blood-corpuscles, 375; Pus, 376. Intestinal Concretions, 376: Bihary, 376; Intestinal CalcuH, 377; Fatty Stools, 378. Crystals of the Feces, 378: Fatty Acids, 378; Charcot-Leyden Crystals, 379; Cholesterin, 379; Hematoidin, 379; Phosphates, 379; Bismuth, 380. Bacteria, 380: Tubercle Bacilli, 380; Pus-producing Organisms, 381; Bacillus of Shiga, 381.

Animal Parasites of the Feces 383

Classification, 383. Gross Examination, 386: Microscopic Study, 387. Intestinal Coccidiosis, 388. Rhizopoda, 388: Amoeba CoH, 388. Flagellata, 392: Cercomonadina, 392; Tetramitina, 392; Trichomonas, 393; Megastoma Entericum, 394; Balantidium Coli, 395. Tape-worms (Cestodes), 396: Taenia SoHum, 398; Taenia Mediocanellata, 399; Dibothriocephalus Latus, 402; Taenia Echinococcus, 404; Taenia Marginata, 406; Hymenolepis Nana, 406; Taenia Cucumerina, 407; Taenia Flavopunctata, 407; Dipylidium Caninum, 407; Taenia Madagascariensis, 409; Taenia Africana, 409; A Questionable Intestinal Parasite, 409; Helophilus, 410; Blue-bottle Fly, 411. Trematodes or Flukes, 411: Fasciola Hepatica, 411; Dicrocoelium Lanceatum, 412; Fasciola Hepatica Angusta, 412; Fasciola Hepatica yEgyptiaca, 412; Fasciola Magna, 413; Distoma Sinense, 413. Round-worms, 414: Ascaris Lumbricoides, 414; Ascaris Mystax, 414; Oxyuris Vermicularis, 414; Uncinaria Duodenale, 415; Trichocephalus Dispar, 418; Strongyloides Intestinalis, 419; Strongyloides Subtilis, 421; Anguillula Intestinalis, 422; Trichina Spiralis, 422.

THE SPUTUM.

Collection 426

Characteristics of the Sputum 428

Microscopic Study of the Sputum 432

Organized Constituents, 432: Fibrinous Coagula, 432; Bronchial Spirals,

CONTENTS.

PAGE

433; Elastic Fibers, 434. Animal Parasites of the Lung, 435: Paragonimus Westermanii, 435; Bilharzia, 436; Amoeba Coli, 436; Trichomonades, 436; Whooping-cough, 436; Taenia Echinococcus, 437; Ascarides, 437; Filaria, 437. Fungi, 437. Bacteria, 438: Tubercle Bacilli, 438; Diphtheria, 442; Influenza, 443; Acute Bronchitis, 443; Chronic Bronchitis, 444; Pneumococcus, 444; Bacillus of Friedlander, 445; Bronchopneumonia, 445; Bronchial Asthma, 445; Pulmonary Abscess, 445; Pulmonary Gangrene and Putrid Bronchitis, 446; Pulmonary Tuberculosis, 447; Incipient Phthisis, 447; Edema of the Lung, 448; Pneumonia, 448; Organic Heart Disease, 449; Pneumoconiosis, 449-

Chemic Study of the Sputum 450

Organic Substances, 450: Proteids, 451; Ferments, 451; Glycogen, 451; Fatty Acids, 451.

BUCCAL SECRETION.

Collection, 452. Physical Properties, 452. Chemistry, 453: Sulpho-

cyanids, 453; Sugar, 453; Diastatic Ferments, 453; Nitrates, 454.

Microscopic Appearance, 454: Epithelium, 454; Bacteriology, 454 Buccal Secretion in Disease

Catarrhal Stomatitis, 455; Ulcerative Stomatitis with Angina, 455;

Gonorrheal Stomatitis, 457; Thrush, 457; Actinomycosis. 458.

Coating of the Tongue 458

Tartar of the Teeth 458

Diphtheria, 459; Pharyngomycosis Leptothricia, 460; Keratosis, 460;

Cultures from the Throat, 461.

NASAL SECRETION.

Naked-eye Appearance, 465; Reaction, 465; Rhodan, 465; Pathologic Secretion, 465; Crystals, 467; Fungi, 467; Entozoa, 467.

DISCHARGES FROM THE EAR AND EYE.

The Ear 468

Parasitic Inflammation of the External Auditory Canal, 469: Detection, 469; Sterigmatocystis Candida, 469. Larv« in the Auditory Canal, 470.

Gonorrheal Conjunctivitis, 470; Keratitis, 471; Trematodes of the Eye, 472; Keratomycosis, 473; Keratoconjunctivitis, 473; Abscess of the Cornea, 474; Diphtheric Conjunctivitis, 474; Trachoma, 475; Acute Infectious Conjunctivitis, 475; Parasitic Cysts, 476.

SECRETION OF THE GENITAL ORGANS.

Semen

Method of Collection, 477; Characteristics, 477; Chemistry, 478; Micro scopic Study, 478. Pathology of the Semen, 480. Vaginal Secretion 481

Microscopic Study, 481. Normal and Pathologic Secretion, 482: Gestation, 483; Bactericidal Properties, 483; Gonorrhea, 483 ; Ulceration of the Cervix, 484; Carcinoma of the Cervix, 484; Diphtheria and Noma, 484; Animal Parasites, 484.

14 CONTENTS.

PAGE

Menstrual Fluid 485

Abortion, 485; Lochia, 485; Vulvitis and Vaginitis, 485; Pruritus Vulvge, 486; Membranous Dysmenorrhea, 486; Vaginal Blennorrhea, 486; Mycosis, 486; Fungi, 486.

TRANSUDATES AND EXUDATES.

Transudates 487

Microscopic Study, 488: Collection, 488; Sedimentation, 489; Fixing, 489; Staining, 489; Cytodiagnosis, 490; Renal Cysts, 490; Ovarian Cysts, 490; Hydatid Cysts, 491; Pancreatic Cysts, 491; Fistulous Secretions, 491.

Exudates 492

Serous Exudates, 492: Inoscopy, 492. Seropurulent Exudates, 492, Chylous Exudates, 493. Hemorrhagic Exudates, 493. Purulent Exudates, 493: Staining, 494; Gonorrhea, 494; Glanders, 497; Anthrax, 497; Tetanus, 497; Leprosy, 497; Animal Parasites, 497; Micrococci, 498; Fungi, 498.

CEREBROSPINAL FLUID AND SYNOVIAL FLUID.

Cerebrospinal Fluid 500

Collection of the Fluid, 500; Staining, 502; Diplococcus IntracellulariS; 502.

Synovial Fluid 504

DISEASES OF THE SKIN.

Forms, 506; Tinea Tonsurans, 507; Tinea Trichophyton Endothrix, 509; Tinea Circinata, 509; Tropic Tinea, 509; Tinea Barbae, 509; Mycotic Dermatitis (Dhobie Itch) 510; Onychomycosis, 511; Gayle, 511; Tinea Versicolor, 511; Erythrasma, 512; Pinta, 512; Blastomycetic Dermatitis, 512; Mycetoma, 512; Myiasis, 513; Vera Macaque, 514; Impetigo Contagiosa, 514; Erysipelas, 515; Eczema, 515; Conditions of Bacterial Origin, 516.

MILK.

Colostrum 517

Human Milk 518

Bacteria, 519. Specific Gravity, 520. Fat, 521. Proteids, 522.

ADDENDA.

Quantitative Estimation of Purin in the Urine 523

Quantitative Estimation of Uric Acid 524

Thermometric Equivalents 526

Weights and Measures 526

INDEX 527

TEXT-BOOK

CLINICAL DIAGNOSIS

CLINICAL DIAGNOSIS.

INTRODUCTION.

THE MICROSCOPE AND ITS USE.

Before attempting to use the microscope the student should place the instrument upon a table in position, and examine it carefully, comparing it with the illustration (Fig. i), and whenever necessary, he should examine the accompanying key in order that he be thoroughly acquainted with this complicated instrument. I am firmly convinced that the chief reason the majority of men fail to obtain satisfactory results with the microscope is that they have neglected to acquire a practical knowledge of the instrument, and to famiharize themselves with the technic necessary for its cHnical adoption.

In clinical microscopy the so-called compound microscope is required; and here it may b^ well to emphasize the fact that it is impossible to do all the forms of clinical work unless the microscope is provided with a two-thirds, a one-sixth, and a one-twelfth oil-immersion objective (Fig. 2) and a substage condenser (Fig. 2). In order to use a one-twelfth objective properly a condenser is absolutely essential — an Abbe condenser is the form usually supplied (Fig. 2, E).

THE DIAPHRAGM.

In a modern microscope the diaphragm (Fig. 2, G) is so arranged as to be readily adjustable. The so-called iris diaphragm is now employed for clinical work and has become an essential feature of the microscope. The particular function of the diaphragm is to cut off all adventitious light, thereby securing illumination of the object in such a manner that the hght upon reaching the microscope is composed of those rays that come from the immediate vicinity of the object only. A diaphragm is further necessary in each substage in order that the aperture may be gaged to suit the different objectives in use, as well as the different 2 17

THE MICROSCOPE AND ITS USE.

objects to be observed. Should light be received directly from a mirror, it is well to have the diaphragm situated as close as possible to the object, in order to prevent all adventitious hght from reaching the object. Again, the diaphragm will be less likely to interfere with illumination from a mirror when it is near the object illuminated. In clinical microscopy the condenser (illuminator, Fig. 2, E) is always to be employed, and for this reason

a further discussiop of the diaphragm appears valueless.

LIGHT.

It is not practicable to employ unmodified light in clinical microscopy, and though it is preferable to obtain light from a northern exposure, this, too, is often impracticable. A northern exposure, when the sky is covered with white clouds, affords a most desirable light, but in this climate the microscopist must complete his work independent of climatic conditions. I have found through experience that a large portion of the microscopic study must be through the use of artificial hght.

A glance at figure 3 will enable the reader to obtain satisfactory light by carefully manipulating the microscope's mirror. When there are vahd reasons for the operator not sitting so as to face the light, it is well to obtain light from over the left shoulder, as is done in reading. Light employed for the microscope is usually spoken of as reflected and transmitted, axial and obhque; these terms designating whether the hght which illuminates a given object traverses such object or is reflected upon it; and whether or not this object is Hghted uniformly or asymmetrically.

Oblique Light. — This is hght in which parallel rays from a plane mirror form an angle with the optic axis of the microscope. Or if a concave mirror or a condenser is used, the hght is oblique

Fig:. I- — I. Huy.c:enian ocular; 2, drawtube, to lengthen or shorten ; 3, main tube ; 4, nose-piece with objectives attached ; 5, objective in position ; 6, stage from which substage is suspended ; 7, substage ; 8, adjustment of substage ; 9, mirror with plain and concave faces ; 10, milled head of coarse adjustment ; 11, screw of fine adjustment.

LIGHT.

when the axial rays of the cone of Hght form an angle with the optic axis (Gage). (See Fig. 3.)

The Getting of Light with the Mirror.— i. Illumination is readily obtained by moving to the left the substage and condenser (Fig. 2), and by placing a mounted specimen upon the

— A

Fig. 2.— Portion of microscope showing substage separated into three parts (C, D, E) : A, Objective; B, adjustment of mechanical stage; F, mirror; G, pivot to adjust iris diaphragm.

microscope stage, and employing a low objective (two-thirds) and a low ocular (Fig. 4).

2. Do not attempt to illuminate the specimen until the objective is lowered to a point about one centimeter distant from the object.

3. Set the diaphragm so that its central opening is approximately the size of the tip of the objective.

THE MICROSCOPE AND ITS USE.

4. Manipulate the mirror (plane surface up) until the light is reflected through the diaphragm to the objective.

5. Whenever the column of light has passed through the diaphragm, an illuminated spot appears immediately beneath the objective; and by looking into the microscope (Fig. 5), the illuminated object is seen. It is unnecessary to explain how the

F"ig. 3.— Diagram of the section of the microscope when in use, showing the rays from the mirror through the condenser to the object, and thence through the lenses of the objective to the real image and through the ocular into the eye. Dotted lines show projected rays from retinal image as the virtual image (A, B).

mirror should be manipulated in order to effect this end, since considerable practical experience is needed.

6. A more brilliant illumination is to be obtained through the use of the concave surface of the mirror, but in using this surface the mirror's position must be at such distance from the object that its focus will be at a level with the object.

LIGHT.

7. It is my custom to advise all beginners in microscopy to obtain light through a low-power objective with a mounted specimen upon the stage of the microscope. The object which serves best for this purpose is a permanently mounted specimen of crystals of uric acid. These crystals are suiSiciently large to be readily seen through a two-thirds objective (Plate 15), and possess sufhcient color to render them conspicuous.

Fig. 4. — Negative eye-piece : d, d, Focal point and diaphragm ; e, 1, eye-lens ; f, 1, field-lens ; e, p, rays entering cornea.

8. The position of the substage, which also governs the position of the diaphragm, is of vital importance in obtaining satisfactory illumination, and a knowledge of this important point is to be obtained only through careful manipulation of the thumb-screw of the substage (Fig. 6), while at the same time the operator closely observes the effect of such manipulation upon the field and object under study.

THE MICROSCOPE AND ITS USE.

FOCUS,

By focusing is meant a bringing of the microscope and the object to be studied in such apposition that a clear image of the object is seen. It will be found that the higher the power of magnification, the nearer must the object be brought to the objective. It is practical, therefore, to note that with the compound cHnical microscope the higher the objective, and the longer the microscope's tube, the nearer the objective must be to the object. Again, unless the oculars be par-focal, the higher the magnification of the ocular, the nearer must the object be brought to the objective. These general principles will serve to guide the be-

Fig. 5. — Manipulation of substage, at same time adjusting iris diaphragm.

ginner, though in a short time actual experience teaches him the distance above the cover-glass, or above the object, at which each objective focuses.

Working Distance. — The distance from the object at which the objective of a compound microscope focuses is referred to as its working distance. This working distance will be found to vary within rather wide Hmits, and such variation will depend upon the power of magnification obtained; in other words, the higher the power of magnification, the shorter the working distance.

FOCUS.

^Z

In view of these optical conditions, the thickness of the cover-glass is of importance, since it may exceed the length of the working distance of the objective employed, in which case it is impossible to focus the object. I have found that the American one-sixth objective has too short a working distance to focus upon the Hnes of a Thoma-Zeiss counting chamber unless a thin cover-glass be employed.

In focusing a one-sixth or an oil-immersion objective the technic differs but sHghtly:

I. Place the shde containing the object to be studied upon the microscope stage, and anchor it with one of the stage clamps.

Fig.

6.— Manipulation of fine adjustment with right hand, and substage with left hand. Tube extended to i6o mm.

2. Place the head in a position so that the eye is on a level with the stage of the microscope, and with the right hand lower the tube by means of the coarse adjustment until it is possible to get but a faint ray of light between the objective and the superior surface of the cover- glass (Fig. 7).

3. The eye is now placed in position at the ocular and the tube of the microscope gently elevated by means of the coarse adjustment. In most instances it requires but a limited amount of practice to enable the student to focus readily after this method.

4. When the object springs into view, the tube is first lowered

THE MICROSCOPE AND ITS USE.

slightly, and again elevated but a trifle, this manipulation being

continued until a fairly clear outline of the object is obtained.

5. The fine adjustment wheel (see Fig. 8) should be rotated

Fig. 7.— Position of operator in focusing.

Fig. 8.— Manipulating fine adjustment with left hand and iris diaphragm with right hand.

slowly, and at the same time the eye be kept in position so as to observe the sHghtest change in the definition.

Caution. — Do not rotate the fine adjustment wheel more than once. It will be found that this wheel, when rotated but a section of the circle, will change materially the definition (clearness

CARE OF THE MICROSCOPE. 25

of the object). Whenever the field of vision becomes dimmed to the sHghtest degree, the fine adjustment wheel should be rotated in the opposite direction.

The Condenser. — The condenser (Fig. 2, E) is necessary in order to do satisfactory microscopic work. When using the flat surface of the mirror, the exact position of the condenser is not of special moment; but practical experience shows that it is possible to employ the concave surface of the mirror to reflect light through the condenser; the distance between the condenser and the mirror, and the object, all become of importance. It is necessary that the operator manipulate the thumb -screw elevating and lowering the substage until the clearest definition is obtained (Fig. 6). Careful adjustment of the substage will be found of inestimable value in bringing out the lines bounding the squares of the Thoma-Zeiss counting chamber.

CARE OF THE MICROSCOPE.

In view of the fact that every microscope is provided with a small booklet giving special directions for its care, it does not appear to be necessary to do more than refer to the subject in this volume.

The location of a particle of dirt that may obstruct or interfere with the view of a certain portion of the field is of practical interest, and will therefore be considered:

1. First, while looking at an object through the microscope rotate the ocular to determine whether or not the particle that obscures the field is rotated; and should the particle rotate, it is situated in the ocular.

(a) Remove the ocular from the tube, and . unscrew for a short distance its upper lens; return the ocular in position and rotate this lens, and should the dirt rotate with the lens, the superior lens only needs cleansing.

(b) The above steps are apphcable to the inferior lens of the ocular.

2. Particles of Hnt and dust may collect upon the condenser, and the location of such dust is determined through the fact that it springs out of focus and returns into focus when the thumb-screw of the condenser is manipulated (Fig. 6).

3. Should the particle of dust remain unchanged after examining both the ocular and the condenser, the student will know that it is situated in the objective. This point may be further determined by screwing the objective to about two-thirds its depth into the nose-piece, and then rotating the objective with

THE MICROSCOPE AND ITS USE.

the eye at the ocular, when the particle of dust will be rotated with the objective.

Cleansing the objective, the lenses of the condenser, and the lenses of the ocular is of great importance in securing clear definition. It is customary to cleanse these lenses with a special paper, and under certain conditions it is allowable to moisten such paper with some Hquid.

Caution. — The lens nearest the tip of the objective is not to be cleansed with xylol, ether, or alcohol. It is my practice to cleanse all lenses of the microscope by the use of a silk or soft linen handkerchief, moistening the handkerchief with sahva. Practice has shown saliva to be the most effectual medium for

Ji.

Fig. 9.— I, Ocular micrometer (natural size) ; 2, scale of micrometer (greatly enlarged).

the removal of oil from the objective. By moistening the finger with saliva and sweeping over the surface of a cover-glass after the use of an oil-immersion objective, the oil is instantly removed from the cover, leaving a highly poHshed surface. Saliva is also a valuable solvent for Canada balsam.

MEASURING OF SPECIMENS.

The measuring of microscopic objects is known as micrometry. It would seem advisable to outHne a method by which even

MEASURING OF SPECIMENS.

the inexperienced may be able to determine the size of certain objects studied. The special apparatus necessary for this purpose is an ocular micrometer (eye-piece micrometer). This apparatus consists of a thin ground glass, upon one surface of which is placed a graduated scale composed of from fifty to one hundred lines (Fig. 9).

The ocular micrometer is placed in the eye-piece upon the diaphragm, graduated side down.