A handbook of the theory and practice of medicine

Front matter

Digitized i

A HANDBOOK

THEORY AND PRACTICE

Preface

In preparing the Fourth Edition of this work, I have again revised it thoroughly, and have endeavoured to bring the information which it contains as nearly as possible up to the present date. The chapters relating to the Absorbent System and the Nervous System have received special attention, and important additional matter has been introduced in connection with these subjects. I trust that the work may still be found adequate to the requirements of Students and Practitioners of Medicine.

THE AUTHOR.

53, Harley Street, November, 1879.

CONTENTS OF VOLUME L

Section I

Chapter Pace I. Introduction — Objects and Method of Study i II. ^Etiology or Causation of Disease ...... 4-

III. Symptomatology or Semeiology — Mode of Invasion or Onset —

Course and Duration — Varieties and Types — Complications and Sequela; — Terminations — Method and Objects of Clinical Examination — Diagnosis — Prognosis . . . . .11

IV. Treatment or Therapeutics 22

Section II

I. Hypenemia or Congestion ........ 25

II. Dropsy — Hydrops 29

III. Haemorrhage 37

IV. Inflammation .......... 42

V. Alterations in Growth — Hypertrophy — Atrophy ... 60

VI. Degenerations — Fatty — Mineral or Calcareous — Fibroid — Pigmentary — Mucoid — Colloid — Albuminoid or Lardaceous

Section III

I. GENERAL DISEASES.

A. Idiopathic Fevers and Allied Diseases.

I. Fever or Pyrexia . . . . . . . . -79

II. On Contagion and Epidemics ....... 94

III. On the Clinical Investigation of Acute Febrile Diseases — On the

Use of the Thermometer . . . . . . .107

IV. Simple Continued Fever — Febricula — Synocha . . . .114

V. Typhus Fever .115

VI. Typhoid or Enteric Fever — Pythogenic Fever — Abdominal

VII. Relapsing Fever — Famine Fever 136

VIII. Scarlatina — Scarlet Fever 141

IX. Rubeola— Morbilli— Measles 149

X. Rotheln — Rubeola Notha — German Measles . . . .154

XI. Variola — Small-pox . . . . . . . . .155

XII. Vaccinia — Cow-pox . . . . . . . . .167

X CONTENTS.

Chapter pACE

XIII. Varicella — Chicken-pox 171

XIV. Erysipelas — The Rose — St. Anthony's Fire . . . .172 XV. Diphtheria 178

XVI. Mumps — Idiopathic Parotitis 187

XVII. Hooping-cough — Pertussis. . . . . . . .189

XVIII. Influenza — Epidemic Catarrh 193

XIX. Epidemic or Asiatic Cholera — Cholera Morbus .... 196

XX. Glanders and Farcy — Equinia — Malignant Pustule . . . 207

XXI. Hydrophobia — Rabies . . . . . . . .210

XXII. Dengue— Dandy Fever - Break-bone Fever .... 214

XXIII. Pestis— Plague 215

XXIV. Yellow Fever 216

XXV. Cerebro-Spinal Ferer — Epidemic Cerebro-Spinal Meningitis . 220

XXVI. Malarial or Paludal Fever — On Malaria or Marsh Miasm —

Intermittent Fever or Ague — Remittent Fever . . . 222

XXVII. On the Diagnosis of Acute Specific Diseases .... 231

B. Constitutional Diseases.

XXVIII. Rheumatism — Rheumatic Fever — Chronic Articular Rheumatism — Muscular and Tendinous Rheumatism or Myalgia — Gonorrhoea! Rheumatism — Rheumatoid Arthritis .... 240

XXIX. Gout— Podagra 252

XXX. Scorbutus — Scurvy 262

XXXI. Purpura 266

XXXII. Rachitis— Rickets 268

XXXIII. Constitutional Syphilis . 275

XXXIV. Tuberculosis— Scrofulosis 280

XXXV. Carcinoma — Cancer— Malignant Disease ..... 290

XXXVI. Diabetes Mellitus— Glycosuria— Diabetes Insipidus . . .295

II. LOCAL DISEASES.

I. Diseases of the Mouth, Tongue, and Salivary Glands — Stomatitis —Glossitis— Ulcers of the Mouth and Tongue — Symptomatic Parotitis or Parotid Bubo — Chronic Enlargement of the Parotid

— Salivation or Ptyalism ....... 308

II. Diseases of the Throat — Acute Inflammatory Affections — Ulcerations— Chronic Affections — Retro-pharyngeal Abscess . . 318

III. Diseases of the Oesophagus — Acute Oesophagitis — Chronic Dis-

eases of the Oesophagus . . . . . . -321

IV. Diseases of the Respiratory Organs— Clininal Phenomena —

Physical Examination — Of the Larynx and Trachea — Of the Chest 336

V. Dyspnoea— Apncea — Cough — Hcemoptysis ..... 365 VI. Catarrh— Coryza 371

VII. Diseases of the Larynx and Trachea — Acute Laryngitis and Tracheitis — Chronic Laryngitis or Laryngeal Catarrh — Ulcers of the Laiynx — Morbid Growths— CEdema Glottidis — Laryngeal Perichondritis — Abscess — Necrosis of the Cartilages — Functional or Nervous Affections ...... 374

Contents

Chapter Page VIII. Diseases of the Bronchi — Acute Catarrhal Bronchitis — Chronic Bronchial Catarrh — Plastic or Croupous Bronchitis — Dilatation

of the Bronchi — Bronchiectasis . . . . . 391

IX. Pulmonary Congestion — CEdema — Haemorrhage .... 403

Chapter I. INTRODUCTION.— OBJECT AND METHODS OF STUDY

In order to acquire a satisfactory knowledge of the Science and Art of Medicine, it is essential that the mental faculties should have been previously cultivated and trained, while at the same time the mind is stored with the requisite information, by an adequate study of the fundamental and more scientific subjects which constitute the earlier portion of the medical curriculum. Above all is it necessary that the student should be thoroughly acquainted with the construction of the human body, and the normal composition, structure, and functions of its various fluids, tissues, and organs in health — in short, with Anatomy and Physiology. Having this information, he will be materially aided in his further progress, if, in the first place, he understands definitely what Medicine includes, and what he is required to learn ; and secondly, if he sets about acquiring the requisite knowledge and skill according to a systematic, orderly, and scientific method.

It will be expedient at the outset to indicate the general scope of the study of Medicine, and to explain the meaning of its more comprehensive scientific terms which are in common use.

Disease. — The study of Medicine may be said to comprehend the study of disease in all its relationships. Under this term is included every deviation from the normal condition of the body or any portion of it, either as regards its structure, state of nutrition, or the due performance of its functions. It will be readily understood that there is no absolute line of demarcation between health and disease, these being merely relative terms. If a disease is associated with any evident structural change, it is said to be organic; if no such change can be detected by any method of investigation with which we are at present acquainted, it is called functional.

Disease requires to be studied from three main aspects, which may be considered under the heads of : — I. Pathology. II. Treatment or Therapeutics. III. Morbid or Pathological Anatomy and Histology.

I. Pathology. In its correct and comprehensive sense pathology signifies that branch of Medicine which deals with and explains the origin, causes, clinical history, and nature of the several morbid conditions to which the human frame is liable. It is divided into : — i. General pathology, which treats of what is common to, or

THEORY AND PRACTICE OF MEDICINE.

bears upon all or a number of diseases; and which includes certain important subjects, such as congestion, hEemorrhage, inflammation, degenerations. 2. Special pathology, which is concerned with the various special and individual diseases. The word pathology has come to be frequently employed in a more restricted sense than that just indicated, viz., as signifying the explanation of the essential nature of morbid processes, of the characteristic changes accompanying the several diseases, and of the pathological causes of symptoms. According to its wider and more correct definition, it will be seen that pathology includes the following subdivisions : —

A. /Etiology or Causation of disease, which treats of the causes of the various maladies, or the influences and agencies by which they are originated.

B, Symptomatology or Semeiology. These terms comprehend the science which is concerned with all that pertains to morbid conditions, whether general or local, in their clinical relations, i.e. as they are represented in the living subject. It has to do therefore with : — i. Their clinical history, including — a. mode of onset or invasion ; b. syjnploms or clinical phenomena ; c. course, dziration, and modes of termination ; d. varieties and types ; e. complications and siquclcE. 2. Their Diagnosis, which signifies the recognition of the seat and nature of particular diseases, and their discrimination from other morbid states. 3. Their Prognosis, or the judgment which is formed as to their future course and ultimate issue.

II. Treatment or Therapeutics. — This important branch of Medicine deals with the principles upon which the management of disease is conducted ; and the measures which are employed with the view of preventing or curing the different maladies, of modifying their progress, or of relieving their attendant symptoms.

III. Morbid or Pathological Anatomy and Histology. — The structural and other recognizable changes which are associated with organic diseases come under this head, as revealed by post-mortem examination.

An useful and adequate knowledge of Medicine can only be built up by studying the subject in all the particulars just indicated. Before proceeding to study individual diseases, it is highly desirable to have a comprehensive acquaintance with the main facts pertaining to general morbid processes, such as are grouped under general pathology. Further, it is essential that all classes of diseases should receive due attention, and that the pathological and clinical relations of different organs and systems to each other should be known. It is a great mistake for the student to confine his observation to any one or more "specialties," even though he may intend ultimately only to practise such ; at the same time there are some of the more special departments which at the present day deserve particular attention.

I proceed now to point out the plan according to which the Science and Art of Medicine can be learnt most easily and satisfactorily. First, a knowledge of its theory should be acquired, as taught in books, lectures, &c, in which such information and ex-

OBJECT AND METHODS OF STUDY.

planations are given with reference to principles and facts as can be conveyed by these methods of instruction. Secondly, the practice of medicine must be learnt: — (i.) By personal observation and examination of actual cases of the several diseases, as exemplified in individual patients, (ii.) By proper attention to the different modes of clinical instruction, in connection with which allusion may be made to the great advantages to be derived from a thorough training in "case-taking," under competent supervision, (iii.) By the education of those external senses which are of such constant service in the investigation of diseased conditions, especially touch, sight, and hearing; and by repeated practice in the employment of the special instruments which are available for a similar purpose, (iv.) By the observation and study of morbid changes produced in the organs and tissues, as disclosed on post-mortem examination, the more minute alterations being ascertained by chemical and microscopic research.

All the methods of study just mentioned are important, though of course those of a practical kind are by far the more so, for anyone who relies on a mere theoretical knowledge of medicine is absolutely incompetent to enter upon its practice. Still this theoretical knowledge is not to be despised, seeing- that it helps materially to clear the way for practical study, and saves a great waste of time and labour, for the student is enabled to comprehend far better what he observes, if he has mastered at least the elements of the subject, and the more information he possesses before beginning his practical work, the more likely is he to derive full and permanent benefit therefrom.

The usual fields for the study of illustrative cases of the several diseases are the wards of a hospital, and the different out-patient departments : each has its advantages and should be duly attended, the former affording illustrations of the acute or more serious chronic affections, the latter of the more common ailments met with in ordinary practice, and of the minor or more localized disorders not usually admitted into hospitals. If practicable, however, it is very desirable that patients should also be visited at their own homes, so that they may be seen surrounded by those conditions which form part of their experience in every-day life. There are certain diseases, moreover, a practical acquaintance with which is of the greatest consequence, which generally can only be studied in this way, viz., the majority of the acute specific fevers, which, with a few exceptions, are not admitted into general hospitals, on account of their infectious nature, and the opportunity is afforded only to a small number of observing them in the special hospitals set apart for these complaints. Though it is requisite, if possible, that examples oi' all forms of disease should be seen, however rarely they may be met with, yet those which are the more common, and which are likely to come frequently under notice in the course of practice, should receive the chief attention, and of these the student cannot observe too many cases, in order to become familiar with all the important facts pertaining to them.

B 2

THEORY AND PRACTICE OF MEDICINE.

Chapter II. /ETIOLOGY OR CAUSATION OF DISEASE

This is a subject of the utmost importance, and demands the most attentive consideration, for an adequate acquaintance with /Etiology is of great value in several respects. It often gives material aid in diagnosis; it not uncommonly throws a light upon prognosis, as the same morbid condition may differ much in its gravity according to its cause ; in the majority of individual cases it affords most useful indications as regards treatment; and, above all, it enables the practitioner to adopt preventive measures against the development or extension of many diseases, and thus to preserve the health of the general community.

A knowledge of ^Etiology implies not only a general knowledge of the causes which are capable of producing disease; but also a more particular acquaintance with the relation between special causes and special diseases, and, so far as this can be obtained, an intelligent comprehension of the manner in which the various influences produce their injurious effects.

It will be readily understood that the same cause may produce many and very different diseases, and vice versa; but with regard to the various classes of disorders, it will be found that each is brought about most commonly by a certain limited number of causes, which act more or less directly on the organ or part affected. This remark may be illustrated by the relation which exists between " taking cold" and lung-affections; between improper food or drirk and derangements of the alimentary canal ; or between excessive mental labour and brain-diseases. Further, the particular causes which give rise to special affections of each organ are still more limited in their range. Some diseases can only be originated by one, definite, specific cause, and to such the term specific is applied.

Numerous terms have been employed to classify causes, often with much ambiguity of meaning. Only those which are practically useful will be alluded to here. The primary division generally made is into proximate and remote. The proximate cause is really the actual morbid condition of any organ or structure upon which the symptoms present depend, and it is synonymous with pathological cause. Remote causes are further divided into predisposing and exciting, some of the latter being named determining.

Predisposing causes include those influences which bring about a condition of the system generally, or of some organ or part, rendering it more prone to become the seat of disease. Exciting causes comprehend the immediate and direct agencies by which the different morbid changes are produced. The term predisposition is used to express the state favourable to the action of. an excitingcause, and the individual in whom it exists is said to be predisposed. It is not to be supposed, however, that there is a distinct and definite limit between the two classes of causes just mentioned ;

.ETIOLOGY OR CAUSATION OF DISEASE.

what may only predispose at one time may excite at another, and especially is this true when several deleterious influences act together and for a long period. Further, a so-called predisposing cause may only render one organ more liable to be attacked with a certain disease than another; for example, age exercises a marked influence as regards the seat of tubercle or cancer.

For the purpose of pointing out the more common causes of disease somewhat in detail, it will be convenient to classify them into: — I. Intrinsic, or those depending upon the individual, in whom they are either inherent or acquired. 2. Extrinsic, or those due to accidental, and chiefly external influences. So far as this is practicable, an endeavour will be made to indicate which may be ranked as predisposing, and which as exciting causes.

I. Intrinsic, a. Age. — A number of diseases are more prone to occur at certain periods of life than at others; while some morbid conditions tend to affect different organs at different ages, or even to be limited to special tissues in the same organ. This may often be explained by the nutritive and functional activity of the system generally, or of certain organs, being much greater at one time of life than at another, and therefore the liability either to general or local disease is more marked. Changes of structure also, in the direction of decay, not unfrequently account for the predisposition due to age, as for example, degeneration of the vessels in advanced life rendering them brittle, and thus leading to cerebral haemorrhage. Young children and persons advanced in years are very subject to ailments of various kinds.

b. Sex. — Females are more prone to certain affections than males, and vice versa, while some diseases are necessarily limited to one or olher sex. This depends on the difference in the conditions of certain organs in the two classes of persons, and in the length of outlets (e.g., the urethra) ; on the functions peculiar to each sex ; on the dissimilarity in habits, occupation, &c ; on the difference in constitutional strength and vigour ; or on certain peculiarities in the nervous system, women being much more sensitive and excitable, and therefore more liable to various nervous disorders. The proportion of deaths is greater among males than females.

c. General or Constitutional Condi 'lion. State of Health, <S°<r. A state of general debility, whether congenital or acquired, predisposes to many diseases. Possibly the opposite condition of robustness and vigour may increase the liability to other affections. The condition of the blood has also much influence, plethoric or anaemic individuals being predisposed to many complaints. Previous diseases, especially those of an acute nature, f requently predispose to or excite others, e.g., the various fevers, hooping-cough, lung-affections, rheumatism, and syphilis. Certain symptoms, such as cough, particularly if neglected, may be productive of serious mischief. Habitual neglect in attending to the natural functions, especially those connected with the alimentary canal, very commonly leads to iujurious results. The existence of morbid changes in certain organs or tissues may readily induce or predispose to further lesions in them, or may give rise to diseased conditions in other

THEORY AND PRACTICE OF MEDICINE.

parts. Thus a fatty or calcified state of the arteries renders them liable to be easily ruptured ; cardiac diseases often excite lung-affections, and vice versa; or one disease of the lung- or heart may originate another. Other causes of disease which may be alluded to under this head are direct loss of blood ; excessive or long-continued discharges ; and the sudden suppression of an habitual discharge, of a chronic skin-disease, or of some local development of a constitutional disorder, such as gout.

d. Temperament. — Four principal temperaments are described, viz., the sanguineous, lymphatic, bilious, and nervous, and each is supposed to indicate a susceptibility to certain particular diseases, though the statements made on this matter are very contradictory, and are often without any foundation in fact. Speaking generally, the sanguineous temperament is believed to predispose to fevers of a sthenic type, active congestion or haemorrhage, and acute inflammations ; the lymphatic to passive congestion, dropsy, low inflammations, and certain constitutional affections ; the nervous to various disorders of the nervous system ; and the bilious to digestive and hepatic derangements.

e. Idiosyncrasy. — Some individuals are affected injuriously by certain agencies, which do not at all influence others in the same way. This is the case with articles of diet, as fish or mushrooms ; or medicines, such as iodide of potassium or quinine. To this individual peculiarity the term " idiosyncrasy" is applied, and it probably has an influence in predisposing to some diseases.

f. Hereditary predisposition. — Several diseases are supposed to be capable of transmission from parent to offspring, and with regard to some of them this belief is unquestionably true, but the evidence is by no means so clear or reliable with respect to others. It must be borne in mind that members of different generations may be exposed to the same extrinsic causes of disease, and this may account for the fact that certain affections seem to run through families. Those maladies or general morbid conditions usually considered to be hereditary include : —

(i.) Certain constitutional or blood-diseases, viz., gout, rheumatism, scrofula, tuberculosis, cancer, syphilis.

(ii.) Some affections of the nervous system, viz., epilepsy, chorea, insanity, hypochondriasis, neuralgia, apoplexy, paralysis.

(iii.) Physical deformities, as well as deficiencies in connection with the special senses, such as blindness or deafness.

(iv.) Early degenerations, either local or general, which are evidenced by degeneration of the vessels, fatty chang'es in organs, loss of the elasticity of the skin, premature greyness or baldness, loss of teeth, and other signs of decay.

(v.) Some skin-diseases, especially psoriasis and lepra.

(vi.) Emphysema and asthma (?).

(vii.) Gravel and urinary calculus.

(viii.) Diabetes.

(ix.) Haemorrhoids (?).

The morbid conditions observed in different generations need not be identical, but may be merely allied in their nature. This jETIOLOGY or causation of disease.

particularly applies to the nervous diseases above mentioned, and to the degenerations. For instance, there may be epilepsy in one generation and insanity in the next. Again, some vicious habit in the parent may lead to disease in the offspring, e.g., intemperance may undoubtedly originate certain nervous disorders. In some cases a constitutional disease in the parent, such as syphilis, may only cause the offspring to be weakly and delicate.

The transmitted disease may be actually developed in the foetus in utero, being then termed congenital ; it may appear spontaneously at some period or other after birth ; or it may lie dormant until brought out by an exciting cause. In some cases it is supposed to pass over one generation and appear in the next, this being called "Atavism."

Hereditary tendency to disease is unquestionably intensified by intermarriage of those suffering from the same affection, e.g., phthisis; and also by the marriage of those who are closely related, very young, or of very unequal ages.

The hereditary character of diseases is sometimes revealed by their development at an earlier age than is usual, of which gout is an instance. Families occasionally seem remarkably prone to be attacked by certain affections, and to have them with great severity, of which the infectious fevers afford illustrations.

g. Race. — There can be no doubt respecting the influence of race in increasing the liability to certain diseases, and vice versa. This is exemplified in the greater proneness of white than black people to suffer from malarial fevers. The prevalence of some diseases among particular races may, however, be explained by their habits, mode of living, and place of abode.

2. Extrinsic a. Causes depending on surrounding conditions.

(i.) Atmosphere. — The air breathed must necessarily influence greatly the state of health, and it does so in the following ways. It may be impure, because it is not sufficiently changed by proper ventilation, and therefore contains an undue amount of the products of respiration and combustion. Or it may be mixed with gases not usually present, such as those which emanate from sewers or decomposing animal or vegetable matters, or those which are given off in connection with many manufactories. Suspended impurities are also often present, e.g., dust, cotton, hair, wool, unconsumed carbon, fragments of metals, arsenic, and, probably, living organisms. The atmosphere is frequently the vehicle for the transmission of specific poisons. The degree of moisture of the air is highly important, excess or deficiency in this respect often producing very injurious consequences. Possibly its electrical condition, or the amount of ozone in it, may have some influence. And, lastly, the degree of pressure of the atmosphere certainly affects the health, of which we have a familiar illustration in the results which sometimes follow the ascent of a high mountain. Atmospheric influences may act either as predisposing or exciting causes of disease.

(ii.) Temperature. — Excessive or long-continued heat or cold, whether acting upon the general system or applied locally, is most injurious. A sudden change from one extreme to the other often

THEORY AND PRACTICE OF MEDICINE.

causes serious mischief, and so does exposure to cold winds. Even in warm weather a "chill" may give rise to disease, and this is frequently due to the patient's own carelessness, for instance, neglecting to change wet clothes, or remaining exposed to a draught when heated and perspiring.

(iii.) Amount of light and insolation. — Those who reside or spend a considerable part of their time where little or no sun-light enters, are unquestionably below par as regards health. The amount and kind of artificial light employed has also some influence in the causation of disease.

(iv.) Soil. — The chief modes in which the soil exercises its influence are by the amount of vegetable matter which it contains susceptible of decomposition ; by its degree of, and permeability to moisture; by its effect on the heat and light of the sun, whether absorptive or reflective ; and by its chemical composition, which affects that of the water and air in the neighbourhood. Wherever there is an accumulation of vegetable substances, with sufficient moisture and a certain temperature, as is the case in marshy districts, malarial affections are almost always prevalent. Clayey soils are very moist and cold. Most sandy and gravelly soils are healthy, unless they contain vegetable matter. Those in which there is a large proportion of lime and magnesia are believed to originate goitre and renal calculus. The breaking up of soil is often attended with evil consequences.

(v.) Sewage. — This is a very common source of disease both on account of the deleterious gases given off from it, and the decomposing org-anic matter of which it consists. In certain cases it contains specific agents in the causation of disease, and promotes their development or renders them more virulent. Sewage materials or the gases which emanate from them are particularly hurtful when mixed with water which is used for drinking purposes.

6. Causes due to the social condition and habits of the individual, and to certain other accidental influences.

(i.) Food.- — This may be deficient in quantity or of improper quality, either habitually or only temporarily, and may thus promote or induce disease, especially in children. On the other hand the diet may be excessive or too rich in quality. Irregularity as regards meals, the habit of bolting food, or insufficient mastication from any cause, are often very injurious.

(ii.) Brink. — Intemperance in the use of alcoholic stimulants is a fertile source of disease, and it is always well to bear this in mind when investigating any doubtful case. Spirits do most harm, especially if taken at frequent intervals, strong or only slightly diluted, and on an empty stomach. It must be borne in mind also that many of the compounds sold as beer, wines, and spirits, contain highly noxious adulterations. Water or the want of it is a very prolific source of disease. When this element is insufficiently supplied for cleanliness and other purposes, serious results often ensue. The habit of drinking large quantities of water, especially during meals, frequently does harm. Again, water may be the direct means of conveying various morbific agents into the system, such as noxious

.ETIOLOGY OR CAUSATION OF DISEASE.

gases, certain salts, poisonous metals, the ova of worms, animal organic matters, particularly those contained in the excrements, vegetable matters in a state of decomposition, and specific poisons. Tea-drinking in excess is a common cause of troublesome symptoms, and its injurious effects are seen daily in all classes of society. Milk does harm if decomposed or adulterated, and it has been definitely proved to be not unfrequently the medium by which specific poisons enter the system.

(iii.) Certain habits, such as smoking or snuff-taking in excess; the use of narcotics, especially opium ; or excessive indulgence in hot condiments, not uncommonly injure the health seriously.

(iv.) Clothing. — This may be insufficient, either habitually or only from time to time ; or certain regions may be inadequately protected. Thus infants and young- children are frequently completely exposed about the lower part of the body, and no doubt " take cold'' as a consequence. The chest is also in many persons insufficiently covered. On the other hand individuals are not uncommonly over-clad, especially children. Clothing may also do harm by being too tight and exerting pressure, as in the case of those who wear tight stays or belts. The habit of neglecting to change clothes when they are wet is very dangerous.

(v.) Want of cleanliness, domestic or personal, often induces disease. Cutaneous affections may arise from the repeated contact with the skin of various substances of an irritating character.

(vi.) Amount of labour and exercise. — Many persons suffer as the result of excessive and prolonged labour, whether carried on habitually or only at intervals. On the contrary, a larger number are injured by leading a sedentary life and taking no exercise. Various occupations furnish instances of both these hygienic errors, though they are often voluntarily indulged in apart from occupation, especially the leading of a sedentary existence.