Chapter V (4)

185. The osseous part of the thigh consists of a single bone, called the femur (fig. XXXIV. 4), the longest, thickest, and strongest bone in the body. It sustains the entire weight of the trunk, and occasionally much heavier loads superimposed upon it. It is constructed in such a manner as to combine strength with lightness. This is effected by rendering the bone what is technically called cylindrical; that is, a bone in which the osseous fibres are arranged around a hollow cylinder. There are two varieties of osseous matter,—the compact, in which the fibres are dense and solid (fig. LXXXVIII. 1), and the spongy, in which the fibres are comparatively tender and delicate (fig. LXXXVIII. 2). Both varieties are, indeed, combined, more or less, in every bone, the compact substance being always external, and the spongy internal; but in the cylindrical bones the arrangement is peculiar. Every long or cylindrical bone consists of a body or shaft (fig. LXXXVIII. 4.), and of two extremities (fig. LXXXVIII. 5). The body is composed principally of compact substance, which on the external surface is so dense and solid, that scarcely any distinct arrangement is visible; but towards the interior this density diminishes; the fibres become distinct (fig. LXXXVIII. 5), and form an expanded tissue of a cellular appearance (fig. LXXXVIII. 5), the cells being called cancelli, and the structure cancellated. In the centre of the bone even the cancelli disappear; the osseous fibres terminate; and a hollow space is left filled up, in the natural state, by an infinite number of minute membranous bags which contain the marrow (fig. LXXXVIII. 3). In the body of the bone, to which strength is requisite, that part being the most exposed to external violence, the compact matter is arranged around a central cavity. By this means strength is secured without any addition of weight; for the resisting power of a cylindrical body increases in proportion to its diameter; consequently the same number of osseous fibres placed around the circumference of a circle produce a stronger bone than could have been constructed had the fibres been consolidated in the centre, and had the diameter been proportionally diminished. The hollow space thus gained in its centre, renders the bone lighter by the subtraction of the weight of as many fibres as would have gone to fill up that space; while its strength is not only not diminished by this arrangement, but positively increased. On the other hand, at the extremities of the bone, space, not strength, is required; required for the attachment and arrangement of the tendons of the muscles that act upon it, and for the formation of joints (fig. LXXXVIII. 5). Accordingly, at its extremities the bone swells out into bulky surfaces; but these surfaces are composed, not of dense and solid substance, but of spongy tissue, covered by an exceedingly thin crust of compact matter, and so, as by the former expedient strength is secured without increase of weight, by this, space is obtained without increase of weight.

A section of the femur, showing, 1. the compact bony substance; 2. the spongy or cancellated structure; 3. the internal cavity containing the marrow; 4. body; 5, extremities of the bone.]

186. The thigh-bone, placed at the under and outer part of the pelvis, has an oblique direction, the under being considerably nearer its fellow than the upper end (fig. XXXIV. 4), in order to afford space for the passages at the bottom of the pelvis, and also to favour the action of walking. The body of the bone, which is of a rounded form (fig. XXXIV. 4), is smooth on its anterior surface (fig. XXXIV. 4), where it is always slightly convex, the convexity being forwards (fig. XXXIV. 4), while its posterior surface is irregular and rough, and forms a sharp prominent line, termed the linea aspera (fig. XXXV. 4), giving attachment to numerous muscles.

187. The superior extremity of the femur terminates in a large ball or head, which forms nearly two-thirds of a sphere (fig. LXXXIX. 4.). It is smooth, covered with cartilage, and received into the socket of the ilium called the acetabulum, which, deep as it is, is still further deepened by the cartilage which borders the brim (fig. LXXXIX. 3). The brim is particularly high in the upper and outer part, because it is in this direction that the reaction of the ground against the descending weight of the trunk tends to dislodge the ball from its socket.

188. Passing obliquely downwards and outwards from the ball, is that part of the femur which is called the neck (fig. LXXXIX. 5). It spreads out archlike between the head and the body of the bone, and is more than an inch in length (fig. LXXXIX. 5). It is thus long in order that the head of the bone may be set deep in its socket, and that its motions may be wide, free, and unembarrassed.

1. Lower portion of the ilium; 2. tuberosity of the ischium: 3. socket for the head of the femur, or thigh-bone; 4. head of the femur; 5. neck of the femur; 6. the great process of the femur called the trochanter major; 7. the body of the femur.]

189. From the external surface of the femur, nearly in a line with its axis, proceeds the largest and strongest bony process of the body which gives insertion to its most powerful muscles, namely, those that extend the thigh and that turn it upon its axis (fig. LXXXIX. 6). Because, from its oblique direction, it rotates the thigh, this process is called the trochanter, and, from its size, the trochanter major. At the under and inner part of the neck on the posterior surface of the bone, is a similar process, but much smaller, called the trochanter minor (fig. XXXV. 4), into which are inserted the muscles that bend the thigh.

190. The inferior extremity of the femur, much broader and thicker than the superior (fig. XC. 1), is terminated by two eminences, with smooth surfaces, termed condyles (fig. XC. 2), which, articulated with the tibia, and the patella, form the joint of the knee (figs. XC. 2, 4, 5, and XCI. 1, 2, 3).

1. Lower end of the femur; 2. condyles of the femur; 3. upper end of the tibia; 4. articular surfaces on the head of the tibia on which the thigh-bone plays; 5. the patella, or knee-pan; 6. upper end of the fibula, not entering into the knee-joint.]

Posterior view of the bones forming the knee-joint. 1. Lower end of the femur; 2. upper end of the tibia; 3. articular surfaces on the head of the tibia, on which the thigh-bone plays; 4. upper end of the fibula, not entering into the knee joint.]

191. The bones of the leg, two in number, consist of the tibia (fig. XC. 3) and fibula (fig. XC. 6). The tibia, next to the femur, the longest bone in the body, is situated at the inner side of the leg (fig. XC. 3). Its superior extremity is bulky and thick (fig. XC. 3). The top of it forms two smooth and slightly concave surfaces, adapted to the convex surfaces of the condyles of the femur (fig. XC. 4, 2). On its outer side there is a smooth surface, to which the head of the fibula is attached (fig. XC. 6). Its lower extremity, which is small, forms a concavity adapted to the convexity of the bone of the tarsus, called the astragalus, with which it is articulated (fig. XCII. 4.) Its inner part is produced so as to form the inner ankle (figs. XCII. 2, and XCIII. 3): its outer side is excavated into a semilunar cavity, for receiving the under end of the fibula, which forms the outer ankle (figs. XCII. 3, and XCIII. 4).

192. The fibula, in proportion to its length the most slender bone of the body, is situated at the outer side of the tibia (fig. XC. 6). Its upper end formed into a head, with a flat surface on its inner side (figs. XC. 6, and XCI. 4), is firmly united to the tibia (fig. XC. 4). Its lower end forms the outer ankle, which is lower and farther back than the inner (fig. XCII. 3, 2).

Anterior view of the bones forming the ankle-joint. 1. Lower end of the tibia; 2. production of the tibia, forming the inner ankle; 3. lower end of the fibula, forming the outer ankle; 4. upper part of the astragalus: these three bones form the ankle-joint; 5 5 5, other bones of the tarsus; 6 6 6 6 6 metatarsal bones.]

Posterior view of the bones forming the ankle-joint. 1. Lower end of the tibia; 2. lower end of the fibula; 3. internal malleolus or ankle; 4. external malleolus or ankle; 5. one of the tarsal bones, called the astragalus, with which the tibia and fibula are articulated; 6. the os calcis or heel.]

193. The patella, or knee-pan (fig. XC. 5), is a light but strong bone, of the figure of the heart as painted on playing-cards, placed at the fore part of the joint of the knee, and attached by a strong ligament to the tibia, the motions of which it follows (fig. XC. 5). It is lodged, when the knee is extended, in a cavity formed for it in the femur (fig. XC.); when bent, in a cavity formed for it at the fore part of the knee (fig. XC. 5).

194. The foot consists of the tarsus, metatarsus, and toes.

195. The tarsus, or instep, is composed of seven strong, irregular-shaped bones, disposed like those of the carpus, in a double row (fig. XCII. 4, 5). The arrangement of the tarsal bones is such as to form an arch, the convexity of which above, constitutes the upper surface of the instep (fig. XCII. 4, 5): in the concavity below are lodged the muscles, vessels, and nerves that belong to the sole.

196. The metatarsus consists of five bones, which are placed parallel to each other (fig. XCII. 6), and which extend between the tarsus and the proper bones of the toes (fig. XCII. 6). Their extremities, especially next the tarsus, are large, in order that they may form secure articulations with the tarsal bones (fig. XCII. 6). Their bodies are arched upwards (fig. XCII. 6), slightly concave below, and terminate forwards in small, neat, round heads, which receive the first bones of the toes, and with which they form joints, admitting of a much greater degree of rotation than is ever actually exercised, in consequence of the practice of wearing shoes. The natural, free, wide-spreading form of the toes, and the consequent security with which they grasp the ground, is greatly impaired by this custom. Taken together, the bones of the metatarsus form a second arch corresponding to that of the tarsus (fig. XCVIII. 2).

197. Each toe consists of three distinct bones, called, like those of the fingers, phalanges (fig. XCVIII.), but the great toe, like the thumb, has only two (fig. XCVIII.). That extremity of the first phalanges which is next the metatarsal bones is hollowed into a socket for the head of the metatarsal bones.

198. Besides the bones already described, there are other small bones, of the size and figure of flattened peas, found in certain parts of the extremities, never in the trunk, called sesamoid, from their resemblance to the seed of the sesamum. They belong rather to the tendons of the muscles than to the bones of the skeleton. They are embedded within the substance of tendons, are found especially at the roots of the thumb and of the great toe, and are always placed in the direction of flexion. Their office, like that of the patella, which is, in truth, a bone of this class, is to increase the power of the flexor muscles by altering the line of their direction, that is, by removing them farther from the axis of the bone on which they are intended to act.

199. The ligaments which connect the bones of the lower extremities are the firmest and strongest in the body. Of these, the fibrous capsule of the hip-joint (fig. XCIV. 1), which secures the head of the femur in the cavity of the acetabulum (fig. XCIV.), is the thickest and strongest. It completely surrounds the joint (fig. XCIV. 1). It arises from the whole circumference of the acetabulum, and, proceeding in a direction outwards and backwards, is attached below to the neck of the femur (fig. XCIV. 1). It is thicker, stronger, and much more closely attached to the bones than the fibrous capsule of the shoulder-joint (144), because the hip-joint is formed, not like the shoulder-joint, for extent of motion, but for strength. Its internal surface is lined by synovial membrane, and its external surface is covered and strengthened by the insertion of muscles that move the thigh-bone. The joint is strengthened by another ligament, which passes from the inner and fore part of the cavity of the acetabulum (fig. XCV.) to be inserted into the head of the femur (fig. XCIV.), called the round ligament, the office of which obviously is to hold the head of the femur firmly in its socket.

1. The fibrous capsule of the hip-joint, laid open and turned aside to show, 2. the round ligament in its natural position.]

A view of the head of the femur drawn out of its socket, and suspended by the round ligament, to show more clearly the action of the ligament in retaining the head of the femur in its socket.]

200. Numerous and complicated ligaments connect the bones that form the knee-joint (fig. XCVI.), and the strength of these powerful bands is greatly increased by the tendons that move the leg (fig. XCVI. 5), which pass over, and more or less surround, the joint.

General view of the ligaments of the knee-joint. 1. Lower end of the femur; 2. upper end of the tibia; 3. upper end of the fibula; 4. the patella; 5. united tendons of the extensor muscles; 6. ligaments of the patella; 7. the capsular investment of the knee; 8. the internal lateral ligament; 9. the external lateral ligaments; 10. the posterior ligament; 11. the ligament connecting the tibia and fibula; 12. a portion of the interosseous ligament.]

201. Strong ligaments maintain in their proper position the bones that form the ankle-joint (fig. XCVII.), connect the bones of the tarsus and metatarsus with one another (fig. XCVIII. 1), and articulate the several phalanges of the toes (fig. XCVIII. 2).

General view of the posterior ligaments of the ankle-joint. 1. Lower end of the tibia; 2. lower end of the fibula; 3. astragalus; 4. os calcis; 5. ligament between the tibia and fibula; 6. ligament passing from the fibula to the astragalus; 7. ligament passing from the fibula to the os calcis; 8. ligament passing from the tibia to the astragalus.]

General view of the ligaments of the sole of the foot. 1. Ligaments connecting the bones of the tarsus; 2. ligaments connecting the bones of the toes.]

202. The joint of the hip, like that of the shoulder, is capable of flexion, extension, and rotation; but its rotatory motions are to a much less extent, on account of the greater depth of the acetabulum and the stronger and shorter fibrous capsule. When the femur is flexed, the thigh is bent upon the pelvis, and its inferior extremity is carried forwards. When it is extended, the thigh is carried backwards. The two thighs may be separated from each other laterally (abduction), or brought near to each other (adduction), or the one may be made to cross the other, and they may be rotated outwards or inwards.

203. The apparatus of muscles that produces these varied motions is seated partly on the trunk and partly on the pelvis. Thus, the powerful muscle that flexes the thigh, or that carries it forwards, termed the psoas (fig. XCIX. 1), arises from the last vertebra of the back, and successively from each vertebra of the loins (fig. XCIX. 1), and is inserted into the lesser trochanter of the femur (fig. XCIX. 3). Its action is assisted first by a large and strong muscle named the iliacus (fig. XCIX. 2), which occupies the whole concavity of the ilium (fig. XCIX. 2), and which, like the psoas, is inserted into the lesser trochanter of the femur (fig. XCIX. 3).

View of the muscles that bend the thigh. 1. The muscle called psoas; 2. the muscle called iliacus; 3. tendons of these muscles, going to be inserted into the trochanter minor of the femur.]

204. The muscles that extend the thigh, or that carry it backwards, named the glutæi, the most powerful muscles of the body, are placed in successive layers, one upon the other, on the back part of the ilium (fig. C. 1, 2, 3), and are inserted into the linea aspera of the femur. They constitute the mass of flesh which forms the hip, and their powerful action in drawing the thigh backwards is assisted by several other muscles (fig. C. 4, 5, 6). Their action is never perfectly simple and direct; for those which move the thigh forwards sometimes carry it inwards, and sometimes outwards; and in like manner, those which move it backwards, at one time carry it inwards and at another outwards, according to the direction of the fibres of the muscle and the position of the limb when those fibres act; while some of them, and more especially those which carry it backwards, at the same time rotate it, or roll it upon its axis.

View of the muscles that extend the thigh. 1. The muscle called glutæus maximus, removed from its origin, 2, 2, to show the muscles which lie beneath it; 2. cut edge showing the origin of the same muscle; 3. the muscle called glutæus medius; 4, 5, 6. smaller muscles, assisting the action of the glutæi.]

205. The knee is a hinge-joint, admitting only of flexion and extension, and is therefore provided only with two sets of muscles, one for bending and the other for extending the leg. The flexors of the leg arise from the under and back part of the pelvis, are seated on the back part of the thigh, and are inserted into the upper part either of the tibia or of the fibula (fig. CI). They consist for the most part of three muscles, named the semi-tendinosus, the semi-membranosus (fig. CI. 3), and the biceps of the leg (fig. CI. 1). The tendons of the two former muscles, in passing to be inserted into the leg, form the inner, and that of the latter the outer, hamstrings (fig. CI. 4, 5).

View of the flexor and extensor muscles of the leg. 1. The biceps of the leg; 2. tendon of the biceps, inserted into the head of the fibula; 3. the semi-membranosus, passing to be inserted into the head of the fibula; 4. tendon of the semi-membranosus forming the inner, and 5. tendon of the biceps forming the outer, hamstring; 6. upper part of the gastrocnemius muscle; 7. the four large muscles which unite to form the great extensor muscle of the leg, inserted into 8. the patella; 9. a portion of the glutæus maximus concealing the other muscles of the hip.]

206. Four large muscles, blended together in such a manner as to form one muscle of prodigious size, termed the quadriceps cruris (fig. CI. 7), occupying nearly all the forepart and the sides, and a considerable portion of the back part of the thigh, constitute the great flexor of the thigh. This enormous mass of muscle arises partly from the ischium, and partly from the upper part of the femur (fig. CI. 7), and is all inserted into the patella (fig. CI. 8), which constitutes a pulley for the purpose of assisting the action of these powerful muscles.

207. The muscles which bend the toes and extend the foot, termed the gastrocnemii (fig. CII. 1, 2), are placed on the back part of the leg, and form the mass of muscle which constitutes the calf of the leg (fig. CII. 1, 2). They arise partly from the lower extremity of the femur (fig. CII.) and partly from the upper and back part of the fibula and tibia; and they form the largest and strongest tendon in the body, termed the tendo achillis (fig. CII. 3), which is implanted into the heel (fig. CII. 4).

View of the muscles which bend the toes, and which, by lifting the heel, extend the foot. 1. The muscle called gastrocnemius externus, which, uniting with 2. the gastrocnemius internus, forms 3. the tendo achillis, which is inserted into 4. the heel.]

View of the muscles which extend the toes and bend the foot. 1. The common extensor; 2. the tendons of the same muscle inserted into the toes; 3. the anterior annular ligament of the foot.]

View of the muscles in the sole of the foot. 1 The muscle which draws the great toe from the other toes; 2. the muscle which draws the little toe from the other toes; 3. the muscle called the short flexor of the toes, which assists in bending the four smaller toes.]

208. The muscles which extend the toes and bend the foot are seated on the fore part of the leg (fig. CIII.); split into tendons like the analogous muscles of the fingers (fig. CIII. 2); and are bound down by a ligament (fig. CIII. 3), exactly the same in name, disposition, and office, as that which belongs to the hand (fig. CIII. 3). Numerous minute muscles are placed in the sole of the foot (fig. CIV.), which act on the toes as the small muscles in the palm of the hand act on the fingers (fig. LXXXVI.).

209. Such are the moving powers which put in action the complicated mechanism provided for the function of locomotion. And these powers are adequate to their office; but they are what may be termed expensive powers; agents requiring a high degree, of organization and the utmost resources of the economy to support and maintain them. Hence in the construction of the framework of the machine which they have to move, whatever mechanical contrivance may economize their labour, is adopted. The construction, form, and disposition of the several parts of that framework have all reference to two objects: first, the combination of strength with lightness; and secondly, security to tender organs, with the power of executing rapid, energetic, and, sometimes, violent motions. The combination is effected and the object attained in a mode complicated in the detail, simple in the design, and perfect in the result. The weight of the body transmitted from the arch of the pelvis to a second arch, formed by the neck of the thigh-bone, and from this, in a perpendicular direction, to a third arch formed by the foot, is ultimately received by the heel behind, and by the metatarsal bones and the first phalanges of the toes before, and more especially by the metatarsal joints belonging to the great and little toe, which have a special apparatus of muscles, for the purpose of preserving steadily their relative situation to the heel. The weight of the body is thus sustained on a series of arches, from which it is, in succession, transmitted to the ground, where it ultimately rests upon a tripod: forms known and selected as the best adapted to afford support, and to give security of position. Columns of compact bone superimposed one upon another, and united at different points by bands of prodigious strength, form the pillars of support. But these bony columns never touch each other; are never in actual contact; are all separated by layers of elastic matter which, while they assist in binding the columns together, enable them to move one upon another, as upon so many pliant springs. The layers of cartilage interposed between the several vertebræ; the layer of cartilage interposed between the vertebral column and the pelvis; the layer of cartilage that lines the acetabulum and that covers the head of the femur; the layer of cartilage that covers the lower extremity of the femur and the upper extremity of the tibia and fibula and the tarsus; the successive layers of cartilage interposed between the several bones of the tarsus; and finally, the layer of cartilage that covers both the tarsal and the digital extremities of the metatarsal bones; are so many special provisions to prevent the weight of the body from being transmitted to the ground with a shock; and, at the same time, so many barriers established between the ground and the spinal cord, the brain and the soft and tender organs contained in the thoracic and abdominal cavities, to prevent these organs from being injured by the reaction of the ground upon the body. The excellence of this mechanism is seen in its results; in contemplating "from what heights we can leap—to what heights we can spring—to what distances we can bound—how swiftly we can run—how firmly we can stand—how nimbly we can dance—and yet how perfectly we can balance ourselves upon the smallest surfaces of support!"

210. It is necessary, in order to complete this general view of the structure of the human body, and of the combination and arrangement of its various parts, to denote the several regions into which, for the purpose of describing with accuracy the situation and relation of its more important organs, the body is divided. It is not needful to the present purpose to describe the regions of the head, because its internal cavity contains only one organ, the brain, and its external divisions do not differ materially from those which are common and familiar; but the chest, the abdomen, and the upper and lower extremities are mapped out into regions, of which it is very important to have an exact knowledge, which may be acquired by the study of the annexed diagrams.

Anterior view of the regions of the body. 1. Region of the neck; 2. region of the chest or thorax. Abdominal regions: 3. epigastric; 4. umbilical; 5. hypogastric region. Regions of the upper extremities. 6. shoulder; 7. arm; 8. elbow; 9. fore-arm; 10. wrist; 11. ball of thumb; 12. the axilla or armpit. Regions of the lower extremities: 13. thigh; 14. knee; 15. leg; 16. ankle; 17. instep and foot.]

Posterior view of the regions of the body: 18. region to the scapula; 19. of the back; 20. of the loins; 21. of the hips; 22. of the ham; 23. of the calf of the leg; 24. of the heel and foot.]

Lateral view of the regions of the body: 25. arch of the foot.]

Anterior view of the situation of the more important internal organs: 1. lungs, right and left; 2. heart; 3. line representing the edge of the diaphragm; 4. liver; 5. stomach; 6. small intestines; 7. colon; 8. urinary bladder.]

Posterior view of the situation of the more important internal organs: 9. kidnies, right and left; 10. the course of the spinal cord.]

Lateral view of the situation of the more important internal organs.]