Elementary physiology for students

Front matter

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Preface

This small manual is an attempt to present to the student of Physiology the leading facts of the science in a fuller way than is generally found in a work of this size.

This has been accomplished mainly by (i) omitting long discussions of rival views and theories, which are a doubtful help to the commencing student, to whom dogmatic teaching is of most value ; (2) by omitting long lists of names (generally polysyllabic) and authorities ; and (3) by introducing very sparingly detailed descriptions of the various complicated machines by which the results recorded have been obtained. The principle that has guided the author in selecting material for the work has been that expressed in these weighty words of Virchow : “ Whoever speaks or writes for the public ought, in my opinion, doubly to examine just now how much of that which he says is objective truth. He ought to try as much as possible to have all inductive extensions which he makes, alt conclusions arrived at by the laws of analogy, however probable they may seem, printed in small type under the general text, and to put with the latter only that which is objective truth.”

It has not been possible to carry out this wise suggestion literally in all cases, but it has been the endeavour, while presenting concisely the latest facts in this science, to omit

VI

Preface.

doubtful theories ; or, at any rate, to insert them in “ small type.” For much in the book the author is deeply indebted to a master of the science, whose luminous teaching first gave him, many years ago, a love of Physiology. It is hoped that the brief and unadorned style necessary to so small a manual may not prevent any from finding the book of some substantial help in the study of this fascinating science.

LIST OF CONTENTS.

CHAPTER. PAGE.

I. The Phenomena of Life i

II. The Elementary Tissues 17

III. Chemical Composition and Metabolism of the

Body 37

IV. On Digestion : —

Section I. — The Carbohydrate or Oral Digestion 52

V. Section II. — The Proteid or Gastric Digestion. 71

VI. Section III. — The Fat or Intestinal Digestion 82

VII. Absorption 95

NTII. The Blood 109

IX. The Blood-Vessels 122

X. The Circulation 134

XI. Body Heat 149

XII. Respiration 155

XIII. The Kidneys 180

XIV. Skin and Fat 199

XV. Muscles 210

XVI. Mechanis.m of the Bones and Muscles . . . 225

XVII. Nerves 237

XVIII. Nerve Centres.— I. The Spinal Cord . . . 254

XIX. Nerve Centres.— II. The Brain. . • . . 269

XX. Sight 305

XXI. Hearing 324

XXII. Voice, Smell, Ta.ste, and Touch .... 333

XXIII. Reproduction 143

LIST OF ILLUSTRATIONS.

Plate I. — Comparative Sizes of Various Tissues and Structures Uniformly Magnified to 8o Diameters.

Plate 2. — Comparative Sizes of Various Tissues and Structures Uniformly Magnified to 240 Diameters {^Frontis.^.

European Skull, showing Facial Angle of 75 degrees, 6

Skeleton with legs apart, 7 Bones of Hand, 8 The Spine, 10

The Bones of Leg and Arm compared, ii Diagram of Arch of Foot, 12 The Two Tubes in the Body, 13 Section, 14

A Cell — Ripe Ovum of Cat, 17 Nuclei, 18

Epithelium of Mouth of Embryo Salamander, 19

Amceboid Movement of a White Blood Corpuscle of Man, 21 Various Body Cells, 23 Various Kinds of Epithelial Cells, 25 Endothelium of the Mesentery of Cat, 25 From a vertical section through the Anterior Layers of the Cornea, 26 From a vertical section through the Epidermis, 26

Plexus of Bundles of Fibrous Tissue from the Omentum of Rat, 27 Tendon of Mouse's Tail, 27 From a Preparation of the Mesentery, 28 From a Preparation of the Omentum of a Guinea-Pig, 28

Hyaline Cartilage of Human Trachea, 29 Fibre- Cartilage of an Invertebral Ligament, 30

From a section through the Epiglottis, 30 Sections of Bone, 32

From a transverse section through the Tibia of Fcctal Kitten, 33 Longitudinal section of Femur of Rabbit, 34

Diet Table, showing p. c. Composition of leading Foods, 48 Alimentary Canal, 53

Diagram of the Digestive Process, 54 The Permanent (above), and Milk Teeth (below), 55

View of Milk Teeth with Germs of Permanent Teeth behind, 55 Half of an Adult Jaw, 55 Longitudinal section through the Praemolar Tooth of Cat, 56 Horizontal and vertical section of a Bicuspid, 56

From a section through a Canine Tooth of Man, 57

Enamel Rods, 58 Diagram of Four Condyles, 59 Section through a Serous or True Salivary Gland ; part of the Human Submaxillary, 63

Section through the Orbital (mucous) Gland of Dog, 64 Acini of Serous Gland, 65 Sub-maxillary, and Sub-lingual Glands and their Nerve Supply, 66 Section of Mouth, Nose, Throat, and Larynx, 67

The Stomach and Duodenum, 71 Peptic Glands from the Cardiac End of the Stomach, 73

From a vertical section through the Mucous Membrane at the Pyloric end of the Stomach, 74 Contents of the Abdomen, 82 From a vertical section through the Mucous Membrane of the Large Intestine "of Dog, 84

From a vertical section through a part of a Human Peyer's Patch, 85 The Duodenum and the Pancreas, 86 From a section through the Pancreas of Dog, 87

A Villus with Fat Globules, 9a

X

List of Illustrations.

From a vertical section through a Fold of the Mucous Membrane of the Jejunum of Dog, 93

Part of a Villus filled with Chyle from the Intestine of a Puppy four days old, 93 The Liver, its Inferior Surface (turned upwards), 96

Blood-vessels of two Lobules of the Liver, 97

The Lymphatics of the Right Arm, lot Lymphatic Vessels of the Diaphragm of Dog, stained with Nitrate of Silver, 102

Stomata, lined with Germinating Endothelial Cells, etc., 103 Developing Lymph-capillaries in the Tail of Tadpole, 104

From a vertical section through a Lymphatic Gland, 105

From a section through a Lymphatic Gland, 106

From a section through the Medulla of a Lymphatic Gland, 107 Human Blood, Fresh, in Hmmoglobin Crystals, 113 Haematin Crystals, 113 Spectra of Blood, 114 Amoeboid IVIovement of a White Blood Corpuscle of Man, 115 Section of Blood-Vessels, Magnified, 122 Minute Microscopic Artery, 123 A Vein and Valves, 124 Diagram of Valves in Vein, 125 Capillaries, Uniting an Artery and a Vein,

Capillaries and Body Cells, 126 Blood Capillar^', 126

Diagram giving an idea of Aggregate Sectional Area of Different Parts of Vascular System, 127 The Aorta and Arch, 128 Transverse section through the Auricle of the Heart ofa Child, 129 Heart with Wall of Left Auricle and Ventricle Removed, 130 Heart with Wall of Right .Auricle and Ventricle Removed, 131 Transverse Section of Heart (from above) showing Valves, 131

Portion of Wall of Left Ventricle and Aorta, 132

The Circulatory System, 134

Syringe illustrating Action of Heart and Valves, 137

i Type of Normal Pulse, 138 Diagram of Heart Beat, 139 Curves Drawn cn a Moving Surface by Three Levers, 140

Malpighian Bodies on an Arterial Twig,

Section of the Spleen of a Rabbit, showing Spleen Pulp, 144

From a section through the ThjToid Gland of Dog, 145

Section through the Thymus. Gland of a Foetus, 147

From a vertical section through the Suprarenal Capsule of Man, 147 Thorax and Contents, 157 Larynx, Trachea, and Bronchi, 158 Lungs and Bronchi, 159 From a longitudinal section through the Trachea of a Child, 160 From a section through the Lung of Cat, stained with Nitrate of Silver, 162 Small Arteries of the Air Cells of the Lungs, 164

Intercostal Muscles, 168 Expansion of Chest and Movement of the Ribs by Action of the Lungs, 169 Diagram of Capacity of Chest, 173 The Kidneys, 180

Course of Urinar>^ Tubule from Malpighian Corpuscle to the Pel\*is, i8x Malpighian Corpuscles from the Cortical Portion of the Human Kidney, 182 Diagram of Course of Uriniferous Tubules in Cortex and Medulla, 183 From a section through the Cortical Substance of the Kidney of a Human Foetus, etc., 184

From a vertical section through the Kidney of Dog, etc., 185

Portion of Convoluted Tubule showing Peculiar Fibrillated Epithelial Cells, 186

From a Vertical section through the Epidermis, 203

Two Tactile Papilla: of the Skin freed of Epithelium, aot

Root of Hair with Surrounding Epidermal Cells, 202

! Transverse section of a Human Hair from ' the Head, with its Follicle, 203

List of Illustrations.

XI

Root and Shaft of Hair, 204 Two Hairs showing Root,'Ctc. , 205 Nail and Matrix in Transverse Section, 206

Human Skin in Vertical Section, 207 Fibres of Heart Muscle, 211 Muscles and Tendon, 212 Muscle Fibres, 213

Muscular Fibre, stained with Haematoxylin, 213

Network of a Striped Muscle, 214 Motor End Plates of Nerves in Striped Muscle, 216

"1 racing of a Single Muscular Contraction of a Frog, 220

Summation of two Stimuli, 221 Incomplete Tetanus, 222 Separate Cells of Smooth Muscle, 223 The Clavicle, 225 Hip-joint (Ball and Socket), 226 Knee-joint (Ginglymus), 227 Three Orders of Levers, 230 The Ligament in front of Hip-joint, 233 Ligaments in Neck, 234 Pad of Cartilage between the Vertebrae, 235 Diagram of Skeleton showing Movement in Walking, 236

Fiom a transverse section through the Sciatic Nerve of the Dog, 238 Transverse section through a Nerve- Bundle in the Tail of Mouse, 239 Non-medullated Fibres, 240 Medullated Nerve-fibres, 240 Meduliated Nerve-fibres, 241 Nerve-fibres of the Cornea, 242 A small Nervous Branch from the Sympathstic of a Mammal, 243 The Sympathetic Nerves, 251 Nerve Cells from the Peripheral Sympathetic Ganglia, 252 The Brain and Spinal Cord, 255 Medulla, Spinal Cord, and Spinal Nerve Roots, 256

Section of Spinal Cord, 257 Transverse section through the Spinal Cord of a Calf, 258

From a transverse section through the White Matter of the Cord, 259 Anterior and Posterior Roots of Nerves, 260

An Isolated Ganglion Cell of the Anterior Horn of the Human Cord, 261

Transverse section of a lateral half of Spinal Cord, 262

Section showing Columns of Cord, 264 Diagram of Rellex Action, 265 External and Sectional View of Brain, 272 Diagram illustrating the Progressive Changes in the Development of the Brain, 273

Diagram of Brain and Medulla Oblongata,

General view of Medulla, 276 Transverse section through the Medulla Oblongata in Region of Pyramidal Decussation, 277

Under Surface of Cerebellum showing Vermiform Process, 278 Transverse section through the Lower Corpus Quadrigeminum, and the Pons Varolii, 281

Surface and Base of Brain, 282 Vertical section through the Grey Matter of a Cerebral Convolution, 283 I Another section of same, 283 : Diagrams of Brain Cells, 284 Lateral Ventricles of Brain, 285 From a vertical section through the Grey Matter of the Cerebellum of the Dog, 288

Side View of Convolutions of the Brain, 294 Diagram of Motor Areas, 295 Lateral View of Medulla showing the position of the Principal Nuclei, 299 Part of the Fifth Cranial Nerve, 301 General Diagram of the Eye, 305 General View of section of Eyeball showing Nerve Supply, 306 From a vertical section through the Anterior Layers of the Cornea, 307 Section of Human Retina, 310 Diagram of (a) the Nervous Elements of the Retina ; and (u) the Connective 'J'issue Substance, 311 Diagram of Visual Angle, 312 Accommodation of the Eye for Distance, Parallel Rays being brought to a Focus on the Retina, 312 Formation of Image on the Retina, 313 Diagram of Alteration of Anterior of Lens in Accommodation, 315 Scheiner's Experiment, 316 Diagram of the Course of the Rays in a Myopic Eye, 317

XU

List of Illustrations.

Diagram of the Course of the Rays n a Hypermetropic Eye, 317 Cones at Yellow Spot, 319 Diagram of the Three Primary Sensations of Colour, 320

Diagram showing Relative Attachments of the Ocular Muscles, 321 Diagram of Eyeballs and Optic Nerves of Part of Pons and Medulla, 322 The Ear, 325

Mechanism of the Ossicula Auditus, 326 Bones of the Ear, 326 Diagram of Outer, Middle, and Inner Ears, 327

The Inner Ear, 328

Sectional and Internal View of Cochlea,328 From a vertical section through the Cochlea of a Guinea-Pig’s Ear, 329 Organ of Corti of the Cochlea of a Guinea-

The Thyroid, Arytenoid, and Cricoid Cartilages, 333

Section of Neck, showmg Larynx, 334

Nerves of Smell, 337

The Tongue,- 338

Filiform Papilla, 339

Fungiform Papilla, 339

A Circumvallate Papilla, 340

Papilla, 341

A Paccinian Corpuscle from the Mesentery of a Cat, 342

An End Bulb of Krause, 342 Corpuscles of Grandry in the Tongue of Duck, 343

Uterus, Vagina, Ovaries, and Fallopian Tube, 345

From a vertical section through the Ovary of a new-born Child, 346 A large Graafian Follicle of the Ovary of Cat, 347

Section of parts of three Seminiferotu Tubules of the Rat, 349 Various kinds of Spermatozoa, 350 A Tubule of the Epididymis in cross section, 351

Penetration of a Spermatozoon into an Ovum, and formation of a Membrane,

Ovum with two Polar Cells and Female Pronucleus, 353

Ovum with Male and Female Pronucleus

Segmentation in the Ovum of Amphioxus, Blastula Stage, 353

Antero-posterior section of the Blastoderm of the Fowl’s Egg before Incubation,

Antero-posterior section of a Fowl's Egg (not incubated), 354

Ovum of Fowl, with Primitive Streak, etc.,

Diagram showing the Gradual Folding off of the Embryo, 355

Diagram showing Early Differentiation ot I I’arts in Blastoderm, 356

Diagram to Show the Mode of Origin of the Amnion, 357

Diagram to Show the Complete Formation of the Amnion, 358

Diagram to Show the Formation of the Allantois, 359

Diagram to Show the Formation of the Placenta, 360

The Villi of the Fmtal Portion of a Mature Human Placenta, 361 Diagram to Show the Early Stages of the Second Embryonic Circulation, 362

Diagram showing the Cur\-ed Form of the Young Embrj-o, 363

Chapter I. The Phenomena Of Life

I. PHYSIOLOGY.

Physiology is one of the subdivisions of Biology, and concerns itself with the functions of life.

Morphology and Embryology^ the other two subdivisions, treat respectively of the forms and development of life.

Physiology also deals with the five leading features of \\iee— birth, growth, development, decay, and five fe.-,. death. . turesoflife.

Birth simply marks the definite commencement of separate e.\-istence, and is an essential of every living thing, in that it implies that all life, without exception, is got by inheritance ; and never since it first originated, as far as we know, has commenced de novo. Before the days of e.xact research, the contrary was believed to be true, and the presence of life in decaying animal and vegetable matter was supposed to prove that life could exist without previous life. It is needless now to show how the progress of science proved this to be a fallacy, and that every form of the lowest bacterium or smallest animal did and could only spring from a parent of the same species. 'Phe theory of spontaneous generation is now everywhere proved to be false, and where adequate care is taken to exclude life

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Elementary Physiology for Students.

from animal matter, no decomposition takes place, and no living forms are found.

Growth is not confined to living beings, but in them it takes place in a totally different way from that Growth. inanimate world. In a crj'Stal, for

instance, or in rock formation, growth takes place by the mechanical addition of layer after layer, the mass itselt taking no part in the process ; and it continues, moreover, indefinitely. In a living organism growth is the result of change and increase in every part throughout the being, and this growth has strict limits beyond which it cannot continue.

Development is a quality that has no parallel in the inanimate world. As growth is an increase in Senf°’’' quantity, so development is an increase in quality, being the perfect adapting of means to ends, of machinery to work, through continual use. Every organ of the body, including the brain, is thus developed by use, and becomes not only larger, but stronger and better adapted for its work.

Decay is now understood to be a constant manifestation of life. It used to be thought that life consisted Decay. ^ powcr to resist decay, and it was only when

life ceased that decay commenced. It is now found, not only that decay is an incessant accompaniment of life from birth, but that it is positively more active during lite than afterwards. It is true that during life the effects of decay are not obvious, as, on the other side of the balance, the opposite force of repair or growth serves as a counterpoise to keep the body in “ dynamic equilibrium ; ” but when the summit of life is passed, repair gets more and more feeble, and at last ceasing in death, leaves the field Irce for the ravages of decay. Life is not, then, a power that resists decay, hut, on the contrary, is a force that canvoi be maniftsled without it; every movement, every look, eveiy

Phenomena of Life.

o thought, involving the decay and destruction of a certain amount of body tissue.

Death is a phenomenon quite peculiar, and necessarily so, to life ; for it is obvious that nothing can cease to live save what has lived. But it is not so much an interruption of life as the final attainment of an end which was held steadily in view from the beginning, and towards which every act of life tended. Exactly as every beat of an eight-day clock is a step towards the final running down of the weights, which is definitely arranged to take place at the end of eight days, so every movement of the l3ody, and every day that it exists, is a step towards that end for which it was constructed ; every body being made, exactly like a clock, to run a definite time. Of course it may be stopped before (as a clock with the finger) by disease or accident. No cause is, however, known why, when the machinery has become perfectly well balanced, and decay and repair are equal, it should not continue so indefinitely, seeing it is self-repairing; instead of wasting away after a certain number of years.

2. LIFE.

^Vhat special power, then, has this life to present such an orderly sequence of phenomena peculiar to itself? What, in short, is life? Life?

Consider for a moment the difference between an egg that IS fertile and can produce a chicken and thus contains life, and one that cannot; for though both are organic compounds, and both produced by living beings, nevertheless they are not the same.

At first sight both eggs appear alike, and, apart from external force, no difference can be seen ; both will go bad, and the living egg will have no advantage over the dead one! But let heat, which is a most potent force, be applied to both, and they will soon begin to differ; and it will be seen in a fe\v

B 2

Elementary Physiology for Students.

days that the “life” in the one egg is a capacity to appropriate and use this force, and eventually to manifest it in the production of a chick ; which chick, in common with all other living beings, must continue to appropriate force in the shape of heat, light, and food, or the life ceases. In the other case the same heat applied to a similar organic substance that does not possess this power or life thus to use it, simply hastens decay and decomposition.

Life, then, is a special power inherent in the living cell to use external force and manifest it in special phenomena, but it is not an independent physical force or energy, being, on the contrary, wholly dependent for its manifestations on

the common forces of nature.

The difference between animal and vegetable life is simple and important. Vegetable life can ap- VegTtabtf propriate force from inorganic matter. It decomposes carbonic acid gas and ammonia, and then stores up the carbon and nitrogen as force to be used hereafter. This life principally consists in the storing of force rather than in its manifestation. Animal life, on the other hand, takes these stores, and in reducing them again to their simple elements of carbonic acid and ammonia evolves and uses up the force they contain. Animal life, therefore, largely consists in the manifestation of energy.

A vegetable may be compared to a hard-working father accumulating large stores of wealth, while the animal rather resembles the spendthrift son who uses it all.

Just, however, as it may be noted that large parts ol vegetables (the layers of bark, etc.) are lifeless, and are subject to such slow changes as to resemble minerals, so within animal bodies many processes are performed by which force is stored and not expended, animal bodies

tlierein closely resembling vegetables.

The animal not only thus uses the force of the vegetable world, but is absolutely dependent upon it, for it is not able

The Exterior of the Body. ■ 5

to use force directly from the inorganic or mineral world, but only after it has been stored and changed by the organic or vegetable.

It may be thought strange that no mention has yet been made of movement as an inherent quality of life, and particularly and obviously of animal life. The truth is that the mere fact of an animal being able to move is not more wonderful than that a steam engine can do the same, and hence movement is no special property of life.

The difference lies in the way in which the transformation of force is effected ; simple and easy to trace in the one, in its steps from the energy in the sunlight transferred to the early vegetation, stored up in our earth as coal, this again passed on to the water as heat, and this as steam passed on to the engine, and resulting in movement by its expansion ; but in the other the actual transformation is at present inscrutable. What is known on the subject will be spoken of later on.

3, THE EXTERIOR OF THE BODY.

Having briefly discussed the question of what life really is, and what are its principal features, and having taken a survey of its various stages, let us now examine an individual as he stands erect before us, and see what we can learn of the human body from an external view.

Notice the shape of the head, the large proportion the brain — which occupies the whole of the head (Fig. i) behind and above a line drawn across the eyebrows and continued to the lobes of the ears — bears to the face, greater than in any animal. Observe that the forehead and the face lie as nearly as possible in the same plane, and the line from the forehead, with that from the ear to the lower edge of upper teeth, forms almost a right

Elementary Piiyriology for Studentr.

angle, an arrangement only suited for the erect attitude, and obviously most inconvenient if man went on all fours, when “ he could see and smell nothing but the ground ” (Holden). As it is, his eyes can command the greatest possible range of vision, their scope being only limited on the inner side by the bridge of the nose, when vision is taken up by the fellow-eye. Observe the eyebrows above, keeping the “sweat of the brow” from deluging the eyes. The eyes should, for beauty, be deeply set, prominent eyes being

never seen in ancient art.

The nose, too, is not placed, as in animals, so as to scent odours in advance, which to them is of the greatest use, but so as to receive odours from below, and especially of all food going into the mouth. The mouth, again, to man is of as much value for articulation in speaking as

Fig. I. — European, Skull showing Facial for eating, and hence the Angle of 75 • prominent,

but the cavities within are specially arranged for the reception and conduction of sound.

Study finally the unique power of e.xpression that lies in the muscles of the face. The science of physiognomy is most valuable and interesting, for undoubtedly these facile muscles get insensibly moulded by the passions and habits of the man, whose character can be fiir better read by the lines round his mouth than by the so-called ‘’expression” of the eye.

The ear, the great beauty of which is its small size and perfect lobe, is not made, as in animals, to turn forwards or backwards to catch distant sounds, man having other means

General View of the Body.

of protection from his enemies and of providing his food than the faculties of scent and hearing.

Observe the lofty forehead, sign of intellect (contrast the head of Shakespeare with the head of one of the Georges), the bright eye of intelligence, the \vellformed nose of strong character, the firm mouth, and the square chin of decision.

Now look at the neck. Note how it is completely formed of muscles (flesh) everywhere but ^ at the throat in front, where you see the prominent “Adam’s apple,” the front of the larynx that contains the voice.

Look now at the body (Fig. 2), and notice generally how all its com-

° . The trunk.

plicated framework and tissues are hidden and so blended as to present but one harmonious whole. Observe that the chest is much broader than it is thick, an arrangement only found, among mammals, in man and some of the highest apes. This arrangement throws the arms much wider apart than the legs, giving them a much wider range .for grasping, but making them weak and useless for walking. In other animals, on the contrary, the upper part of the chest is narrow', to allow the forelegs to come close together and stand directly under the trunk they support. Notice the bony framework of the chest, which is formed by the ribs and breastbone. Observe that if these w'ere continued all the way down, we could not stoop, and could hardly move. The lower half of the body, therefore, is protected instead by a firm Init yielding wall of strong muscles; added to which are. some elastic fibres. In

Fig. 2. — Skeleton with legs apart. When together, the slant of the thighbones is clearly seen.

Elementary Enys/olocy for Students.

animals who walk on all fours these fibres form a complete elastic belt to support the body. Note, moreover, that the heaving of the chest and beating of the heart are all conducted within the thorax, so that the three great organs necessary to existence — the brain inside the skull, the lungs and the heart beneath the ribs — are thus entirely protected from all ordinary injury.

We have alluded to the bony framework, and we may weight of the body. Note that the forearm does not fold on the upper arm, but to its inner side towards the mouth, a more useful position. Look at the hand and wrist (Fig. 3), which alone contain some twenty-seven bones. The supple strength of the wrist ; the value of the thumb, not placed in a line with the otlfcr fingers, but in advance of them, and so as to touch them all ; the nails arranged to support the fingertips, and yet not interfere with their touch, are worthy of note. The hands are marvels of precise and adapted echanism, capable, not only of executing every variety note one or two facts divide the body into seven parts — four limbs, trunk, and head and neck — we find each part contains about thirty bones (counting the ribs in pairs), there being about two hundred in all the body. These bones form the framework of the body, and on their length depends the height of the man.

Fig. 3, — leones of Hand.

Observe, now, the arm generally : The looseness Ji!d riand™ shoulder-joint,

adapted for universal movement, but not to sustain the

Proportions of the Body.

o work, of expressing many emotions of the mind, but of executing its orders with inconceivable rapidity.

Take, now, a wider view of the beauty of the human figure. Let the person stand with feet together and outstretched arms. His breadth is now of°he’Body equal to his height, and the four sides of a perfect square will in a perfect figure touch the soles of the feet, the crown of the head, and the tips of the fingers. Of the height, the hand should measure one-tenth part, the forearm one-quarter, the head one-eighth, the face one-tenth, the leg (from knee-cap to foot) the same, while the greatest width of the chest should measure one-fifth, the least one-sixth ; the breadth of the nostrils should equal the length of the eye j the mouth should be half as long again ; the forehead should be the same breadth as the nose is long. Coming down the trunk, observe that the rugged outlines in statuary in the male figure are all due to muscular development, indicating strength; while the smoother curv'es of the female figure are due to the preponderance of fat. Observe, by the way, how every part is so moulded thaf those forms, the commonest in human designs and machines, straight lines and angles, hardly exist in the body at all. In the erect position one of the beauties of the body is its perfect balance, and the way it conforms to the laws of gravitation.

Notice, now, that the waist is a natural, and not an artificial, product, but that it forms, as we have said, not an abrupt angle, but a hollow curve JndBack' from above downwards ; and an ellipse, and not a circle, horizontally. Observe that in the male figure the shoulders are rather broader, and in the female slightly narrower than the hips ; so tliat the male form somewhat resembles a single inverted cone, the female a double one. Notice how broad and strong the haunch-bones are as compared with animals, since it is only in the erect position they have largely to bear the weight of the internal organs.