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| ISBN-13: | 9780486144023 |
|---|---|
| Publisher: | Dover Publications |
| Publication date: | 07/10/2012 |
| Series: | Dover Anatomy for Artists |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 624 |
| File size: | 56 MB |
| Note: | This product may take a few minutes to download. |
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A Handbook of Anatomy for Art Students
By Arthur Thomson
Dover Publications, Inc.
Copyright © 1964 Dover Publications, Inc.All rights reserved.
ISBN: 978-0-486-14402-3
CHAPTER 1
THE INFLUENCE OF POSTURE UPON THE FORM OF MAN
'MAN alone stands erect.' The least observant amongst us cannot have failed to recognize the fact that man owes much of his dignity to the erect posture. In this respect he differs from all other animals. If we compare him with the manlike apes, his near relations, they suffer much by contrast. The gait of these creatures is shuffling, and the balance of the figure unsteady; while their whole appearance, when they attempt to walk upright, suggests but a feeble imitation of the grace and dignity of man's carriage.
The assumption by man of the erect position has led to very remarkable changes in the form of his skeleton and the arrangement and development of his muscles.
In his growth from the ovum to the adult, he passes through many stages. In some of these his ascent from lower forms is clearly demonstrated. This statement holds good not only in regard to structure, but also as regards function.
To take a case in point. The child at birth is feeble and helpless, and the limbs are as yet unsuited to perform the functions they will be called upon to exercise when fully developed. Dr. L. Robinson has clearly proved that the newborn child possesses a remarkable grasping power in its hands. He found that infants, immediately after birth, were able to hang from a stick, for a short time, by clutching it with the hands. With this exception, we may regard the movements of the limbs as ill controlled and imperfect. At first the legs are not strong enough to support the body. It is only after a considerable time has elapsed that the child makes efforts to use them as means of progression. These first attempts are confined to creeping, an act in which the fore limbs play as important a part as the hind. With advancing age, however, the legs become longer and the muscles more powerful. In course of time they are sufficiently strong to support the body-weight. In the earlier stages of the assumption of the erect posture the child assists itself by laying hold of any object which it can conveniently grasp with its hands; as yet its efforts are ungainly and unsteady, but practice, and the exercise of a better control over the muscles of the legs, soon enable it to stand upright and walk without the aid of its upper limbs.
There are thus three stages in the development of this action : first, the use of 'all fours'; secondly, the employment of the upper limbs as means to steady and assist the inadequately developed lower limbs—this mode of progression is comparable to that of the man-like apes; and, thirdly, the perfected act wherein the legs are alone sufficient to support and carry the body.
The growth and development of the legs are not the only changes that are associated with the assumption of the erect position. If the back-bone of an infant at birth be examined and compared with that of an adult, other differences than those of size and ossification will be observed. As will be afterwards explained, the adult back-bone is characterized by certain curves, some of which we fail to notice in the child. These latter, therefore, are developed at a period subsequent to birth, and are described as secondary curves, whilst those which exist at birth and are maintained throughout life are called primary curves. The primary curves are those associated with the formation of the walls of the great visceral cavities, whilst the secondary curves are developed coincident with the assumption of the erect position, and are compensatory in their nature. The advantage of this arrangement is that the curves are not all bent in the same direction, but alternate, so that the column is made up of a succession of backward and forward curves. In this way the general direction of the back-bone is vertical, which it could not possibly be if the curves did not so alternate, for then all the curves would be directed forwards, and a vertical line would fall either in front of, across, or behind the bent column in place of cutting it at several points, as happens in the column with the alternating curves. This becomes a matter of much importance when the vertical line coincides with the direction of the force exercised by gravity, as in standing upright.
These facts may be proved by looking at a baby. The back displays a uniform curve from the shoulders to the hips; as soon as the child begins to walk, however, the development of a forward curve in the region of the loins is observed, a curve which ultimately becomes permanent and is associated with the graceful flowing contours which are characteristic of the back of the adult. This lumbar curve is one of the most remarkable features of man's back-bone, for, although the curve is exhibited to a slight extent in the columns of the apes, in none does it approach anything like the development met with in man. On the other hand, in four-footed animals, where the column is horizontal in position, there is either no such curve present, or it is only slightly developed.
The assumption of the erect posture necessarily involves the growth of powerful muscles along the back to uphold and support the back-bone and trunk in the vertical position, as is proved by the changes which take place in old age. At that time of life the muscular system becomes enfeebled, and is no longer strong enough to hold the figure erect; the consequence of which is the bent back and tottering gait of the aged, who, in their efforts to avail themselves of every advantage, seek the assistance which the use of a staff affords. Thus history repeats itself within the span of our own existence. It has been seen how the young child avails itself of the assistance of its upper limbs in its first attempts to walk; and it is noteworthy how, in that 'second childhood', the weak and aged seek additional support by the use of their arms and hands.
It is, however, to neither of these types that our attention must be especially directed, but rather to the examination of man in the full exercise of his strength, after he has outgrown the softness and roundness of youth, and before he has acquired any of the weakness dependent on advancing years.
Starting, then, with the fundamental idea that the erect posture is essentially a characteristic of man, it is necessary to study in some detail the various modifications in his bony framework and muscular system which are associated with this posture.
As a vertebrate animal, man possesses a back-bone or spinal column made up of a series of bones placed one above the other. Around this central column are grouped the parts of the skeleton which protect and support the trunk. On the upper end of this axis is poised the head, and connected with the trunk are the two pairs of limbs—the arms and legs.
For convenience of description it will be necessary to consider the body in its several parts:
1. The trunk.
2. The lower limbs.
3. The upper limbs.
4. The head and neck.
In regard to the trunk, as has been already stated, the vertebral column, so called because it is composed of a number of separate bones or vertebrae, forms the central axis around which the other parts are grouped. Comparing the position of this chain of bones in man with that observed in a four-footed animal, it will be noted that in man its axis is vertical, whilst in a quadruped it is more or less horizontal; moreover, the column in man is curved in a more complex manner than is the case in animals. It is on these curves that the column is mainly dependent for its elasticity. It would, however, be unable to sustain the weight of the trunk unless some provision had been made whereby it could be held erect. This is supplied by the powerful groups of muscles which lie in the grooves on either side of, and behind, the back-bone. An inspection of the back of a model will enable the student to recognize these fleshy masses on either side of the middle line, particularly in the lower part of the back, in the region of the loins. These groups of muscles are called the erectores spinae, a name which sufficiently explains their action, and may well be compared to the 'stays' which hold a mast upright. How much depends on the action of these muscles is, as has been said, amply demonstrated in the case of the feeble and aged, in whom the muscles are no longer able properly to perform their function, with the result that the persons so affected are unable to hold themselves erect for any time without fatigue.
The column supports the weight of the head, and by its connexion with the ribs, enters into the formation of the chest-wall. The upper limbs are connected with the chest-wall in a way which will be subsequently described. It is thus evident that this central axis is a most important factor in the formation of the skeleton of the trunk. Through it the entire weight of the head, upper limbs, and trunk is transmitted to the lower limbs, which necessarily have to support their combined weight in the erect position.
It is to the structure of these limbs that our attention must next be directed. In considering them it must be borne in mind that the legs serve two purposes: first, they afford efficient support, and, secondly, they are adapted for the purposes of progression. The limbs are connected with the trunk by means of bones arranged in a particular way. These are termed the limb girdles. There are two such girdles—the shoulder-girdle, connecting the upper limbs with the trunk, and the pelvic girdle, connecting the lower limbs with the trunk. As the latter is concerned in transmitting the weight of the trunk to the lower limbs, it is well first to examine it.
From its function it is essential that the pelvic girdle should be firmly united to the vertebral column or central axis by means of an immovable joint. In order to effect this union the segments or vertebrae, of which the column is made up, undergo certain modifications in the region where the girdle-bones of the lower limb are attached. This modification consists in the fusion of a number of these vertebrae, which are separate in the infant, and their conversion into one large wedge-shaped bone called the sacrum. This bone, built up by the union of five vertebrae, is, in man, remarkable for its width and stoutness. It acts not only as a strong connecting link between the vertebral column and the bones of the pelvic girdle with which it articulates, but also provides a fixed base on which the upper and movable segments of the central axis are placed. The posterior aspect of the sacrum also furnishes an extensive surface for the attachment of the erector muscles of the spine, which assist so materially in maintaining the column in its erect position. The bones of the pelvic girdle, though separate at an early period of life, are in the process of growth fused together to form a large stout irregular bone called the haunch-bone (os innominatum). There are two such bones—one for either limb—and these are united behind to each side of the sacrum by means of an immovable joint. The girdle is further strengthened by the union of the two bones with each other in the middle line in front, where they are bound together by an immovable joint called the synaphysis pubis. A bony basin, called the pelvis, is thus formed by the articulation of these two haunch-bones in front, and their union with the sacrum behind. There is no movement between the several parts of this osseous girdle, and it is firmly united with the lower part of the vertebral column. It helps to form the lower part of the trunk, and, by its expanded surfaces, assists materially in supporting the abdominal contents. This form of pelvis is very characteristic of man. As a result of the assumption of the erect posture the abdominal viscera are no longer supported entirely by the abdominal walls, as in four-footed animals, but rest to a very considerable extent on the expanded wings of the pelvic bones. In addition, the outer surfaces of these expanded plates of bone are utilized to provide attachment for the powerful muscles which pass from and connect this pelvic girdle with the thigh-bone, a group of muscles which in man attains a remarkable development.
The fact must be emphasized that no movement is possible between the pelvic girdle and the sacrum, and that all the weight transmitted down the vertebral column through the sacrum is equally distributed between the two haunch-bones.
If the outer surface of each of these bones be examined, a deep cup-shaped cavity will be noticed, into which the rounded head of the thigh-bone or femur fits, thus forming the movable articulation called the hip-joint. The bones of the thigh and leg are remarkable for their length. Combined they equal in length the measurement of the head and trunk. This relative development is not attained by any other animal. In addition, the thigh bone of man possesses an extremely long and well-marked neck. The neck is that part of the bone which supports the rounded articular head, and connects it in an oblique direction with the upper end of the shaft. The length of the neck of the femur is peculiar to man, and permits a freedom of action of the limb not attainable by any other animal, the movements in the lower animals being more or less limited to a backward and forward direction. By means of the neck of the thigh-bone we have in man an arrangement which fulfils all the conditions necessary to ensure stability, and permits a more extended range of movement, not only from before backwards and from side to side, but also in an inward and outward direction. This latter is the movement of rotation, whereby we are enabled to turn the front of the limb inwards or outwards as desired.
The muscles to which reference has been already made in connexion with the outer surfaces of the haunch-bones are inserted into the upper part of the thigh-bone. As they are immediately concerned in the control of certain important movements of the hip-joints, through which the entire weight of the trunk is transmitted to the lower limbs, they necessarily acquire a very great development, a development on which is dependent the prominence of the buttocks. This appearance was justly regarded by Aristotle as eminently characteristic of man.
The thigh-bones, separated above by the width of the pelvis, are placed obliquely so that they lie side by side in the region of the knees.
The bones of the leg are two in number. They are immovably united to each other, since any movement between them would interfere with their stability and thus weaken the limb as a means of support. One only of these bones, the shin-bone or tibia, enters into the formation of the knee-joint; by its expanded upper extremity it affords a broad surface not only for the support but also for the movements of the condyles, or articular surfaces, of the thigh-bone. The slender outer bone, the fibula, furnishes extensive attachments for numerous muscles.
The fleshy masses which move the leg on the thigh at the knee-joint clothe both the front and back of the thigh-bone; in man the extensor group of muscles, viz. that placed on the front of the thigh, which extends or straightens the leg, attains a relatively greater development than the flexor group, which is situated on the back of the limb. This is just the reverse of what is found in animals, and is associated in man with the power he possesses of bringing his leg into a direct line with his thigh, that is to say he can straighten or extend his limb at the knee-joint in a way which no other animal can effect.
Man's foot is a very characteristic member. It possesses the qualities essential to strength and solidity combined with elasticity and movement. When standing upright the axis of the foot is placed at right angles to the axis of the leg.
The bones which enter into the formation of the foot are disposed so as to form a series of arches. The advantage of this arrangement is that the soft parts on the sole are protected from pressure, while at the same time considerable elasticity is imparted to the foot. The slight play of the bones which form the arches allows the latter to act like a series of curved springs.
The form of the heel-bone, or os calcis, is characteristic: to its posterior part is attached that group of muscles which determines the form of the calf. The development of these muscles is very great; and it is noteworthy that they are quite typical of man, as no animal equals him in this respect. This is explained by the fact that not unfrequently they are called upon to support the entire weight of the body, as in the acts of standing or dancing on tiptoe, while at other times they are required to project the body forward, as in springing or leaping.
(Continues...)
Excerpted from A Handbook of Anatomy for Art Students by Arthur Thomson. Copyright © 1964 Dover Publications, Inc.. Excerpted by permission of Dover Publications, Inc..
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents
CHAPTER I. THE INFLUENCE OF POSTURE ON THE FORM OF MAN.Early attempts at walking
Curves of back-bone
Vertebral column
Erectores spinae
Limb girdles
Pelvic girdle
Thigh-bone
Skeleton of lower limb
Leg and foot
Shoulder-girdle
Form of chest-wall
Skeleton of upper limb
Skull
CHAPTER II. GENERAL DESCRIPTION OF THE BONES AND JOINTS.
Classification of bones
Chest-wall
Joints
Movable joints
Immovable joints
CHAPTER III. VERTEBRAL COLUMN OR SPINE.
Vertebral column
The vertebrae
Curves of column
Curves of back
Grooves for muscles
Erector spinae
Movements of column
"CHAPTER IV. THE THORAX, THE REGIONS OF THE FLANK, AND THE ANTERIOR ABDOMINAL WALL."
Ribs
Breast-bone
Thorax
Anterior abdominal wall
Haunch-bone
Lumbar aponeurosis
External oblique
Rectus abdominis
Contours of abdominal wall
Fold of groin
Differences between male and female
The flank
Action of abdominal muscles
Effect of movements on contours of abdominal wall
CHAPTER V. THE SHOULDER-GIRDLE AND THE MUSCLES WHICH INFLUENCE ITS MOVEMENTS.
Shoulder-girdle
Collar-bone
Shoulder-blade
Girdle as a whole
Direct and indirect action of muscles
Trapezius
Rhomboids
Action of trapezius
Serratus magnus
Action of serratus magnus
Rotation of scapula
Humerus
Shoulder-joint
Latissimus dorsi
Pectoralis major
The breasts
Deltoid
Action of the deltoid
Infra-spinatus and teres minor
Teres major
Summary of the muscles of the back
The female back
CHAPTER VI. THE UPPER ARM.
The armpit
Coraco-brachialis
Humerus
Bones of fore-arm
Ulna
Radius
Elbow-joint
Fascia of upper arm
Brachialis anticus
Biceps cubiti
Triceps
Anconeus
External intermuscular septum
Internal intermuscular septum
CHAPTER VII. THE FORE-ARM.
Pronation and supination
Wrist-joint
Bones of the wrist
Movements of the wrist-joint
Pronators and supinators
Muscles of the fore-arm
Flexors of the wrist
Superficial flexor of the fingers
Supinator longus
Radial extensors
Ulnar extensor
Ulnar furrow
Common extensor of the fingers
Depression behind elbow
Extensors of thumb
Summary of the muscles of fore-arm
Surface contours of fore-arm
Hollow in front of elbow
Influence of position on form of fore-arm
Contours around elbow
Superficial veins of arm
Front of wrist
Action of muscles
CHAPTER VIII. THE HAND.
The skeleton of the hand
Joints of the fingers
The thumb
Short muscles of the thumb
Abductor indicis
Muscles of the little finger
The palm
The fingers
Back of the hand
Movements of the fingers
Summary
CHAPTER IX. THE GLUTEAL REGION.
Skeleton of the lower limb
Innominate bone
The ilium
Pubis
Sacrum
Pelvis
Femur
Obliquity of the thigh-bones
The hip-joint
Ilio-femoral ligament
Mechanism of erect posture
Obliquity of the pelvis
Influence of pelvic obliquity on thigh
Movements of the hip-joint
Gluteus maximus
Gluteal fold
The buttock
Actions of gluteus maximus
Tensor fasciae femoris
Ilio-tibial band
Gluteus medius
Anterior superior iliac spine
Surface forms of buttock
CHAPTER X. THE THIGH.
The femur
Bones of the leg
The tibia
The fibula
The patella
Knee-joint
Movements of knee-joint
Locking of the knee-joint
Muscles of the thigh
Extensor muscles
The vasti and rectus
Sartorius
Adductor muscles
Gracilis
Action of adductors
Flexor muscles
The hamstrings
Action of hamstrings
Form of female thigh
Hip-width
Contours of thigh
Straightness of limb
Form of knee
CHAPTER XI. THE LEG AND FOOT.
Bones of leg
The ankle
Bones of the foot
Astragalus
Os calcis
Ankle-joint
Muscles of leg
Tibialis anticus
Long extensor of the toes
Peroneal muscles
Muscles of calf
Tendo Achillis
Action of muscles of calf
Surface contours of leg
The back of the knee
Form of leg in female
Bones of the foot
Arches of the foot
Dorsum of the foot
Short extensor of the toes
Muscles of the foot
Plantar fascia
Sole of the foot
The toes
Female foot
Superficial veins of leg
CHAPTER XIII. THE NECK.
The atlas and axis
Movements of the neck
Muscles of the neck
Ligamentum nuchae
Deep structures of neck
Hyoid bone
Larynx
Thyroid body
Sterno-mastoid muscle
Pit of the neck
Hollows above the collar-bone
Action of sterno-mastoid
The platysma
Contours of neck
Length of neck
Movements of neck
Neck and shoulders
"CHAPTER XIII. THE HEAD, FACE, AND EXPRESSION."
The skull
Bones of the skull
Frontal sinus
Cranium
Size of head
Bones of face
The facial angle
The lower jaw
The masseter
Form of lower jaw
The chin
The orbits
Nose
Ear
Mouth
Eyes
Expression
Muscles of expression
The eye in expression
Muscles of the nose
Muscles of the mouth
The mouth in expression
Laughter
Reflection
Shyness
Rage
Sneering
Disdain
Fear
Horror
Habitual expression
CHAPTER XIV. PROPORTION.
Proportion
Proportions of female
Female figure
Proportions of child
Growth
Old age and decay
APPENDIX
INDEX