274 OSTEOLOGY. 



shaft distal to the greater trochanter, as well as from the inner surface of the thin but compact 

 outer shell of the upper surface of the neck, the whole forming a bracket-like arrangement which 

 assists materially in adding to the strength of the neck. Further support is afforded by the 

 addition of a vertical layer of more compact bone within the spongy tissue of the neck. 

 Distally, as may be seen in Fig. 278, this is. continuous with the dense posterior wall of the body 

 below ; whilst proximally it sweeps up beneath the lesser trochanter, from which it is separated 

 by a quantity of loose spongy tissue, to fuse proximally with the posterior dense wall of the 

 neck above and medial to the intertrochanteric crest. It may be regarded as a continuation 

 proximally of the posterior wall of the body beneath the trochanteric epiphysis. When 

 studied in section (see Fig. 279), the central dense core of this partition exhibits a spur-like 

 appearance : hence the name calcar femorale applied to it. It is of surgical importance in cases 

 of fracture of the neck of the femur. (R. Thompson, Journ. Anat. and PhysioL, vol. xlii. p. 60.) 

 From it, stout lamellae having a vertical direction arise. The spongy tissue of the head and 

 greater trochanter is finely reticulated, that of the distal part of the neck and proximal part of 

 the shaft being more open in its texture. Passing vertically through this tissue there is a 

 vascular canal, the orifice of which opens externally on the floor of the trochanteric fossa. 



The spongy tissue of the distal part of the body is more delicate and uniform in its 

 arrangement, displaying a more or less parallel striation in a longitudinal direction. Subjacent 

 to the articular surface the tissue is rendered more compact by the addition of lamellae disposed 

 in curves in harmony with the external aspect of the bone. 



The Patella. The bone consists of a thick dense layer anteriorly, which thins towards the 

 edges on either side and distally ; proximally, it corresponds to the area of insertion of the quadriceps. 

 The femoral articular surface is composed of a layer of compact bone, thickest in correspondence 

 with the vertical elevation. Sandwiched between these two layers is a varying thickness of 

 spongy tissue of fairly close grain, the striation of which on cross section runs in parallel lines 

 from back to front ; on vertical section the tissue appears to be arranged in lines passing radially 

 from the deep surface of the femoral area to the more extensive anterior dense plate. 



The Tibia. The body of the bone is remarkable for the thickness and density of the 

 osseous tissue which underlies the anterior crest. The posterior wall is stout, but the medial and 

 lateral walls are thinner. The several walls are thickest opposite the middle of the body, and 

 thin out proximally and distally where the body unites with the epiphyses. The medullary 

 cavity, narrow and circular in the middle of the bone, increases in all its diameters proximally and 

 distally, and reaches to within 2^ to 3 inches of either extremity. Proximally the arrangement 

 of the lamellae of the spongy tissue resembles a series of arches springing from the dense outer 

 walls. These form a platform on which the proximal epiphysis rests, the spongy tissue of which 

 displays a more or less vertical striation. This is much more compact under the condylic 

 surfaces, the superficial aspect of which is formed by a thin layer of dense bone. The intercon- 

 dyloid eminence and the tuberosity are also formed of compact tissue, whilst the circumference of 

 the condyles is covered by a thinner and less dense wall. In the distal end of the body the spongy 

 tissue, of a loose and' cellular character, is arranged in vertical fibres, blending with the closer 

 tissue of the distal epiphysis, the articular surface of which is covered by a thin but dense layer. 



In the adult bone the nutrient canal for the body is embedded in the dense posterior wall for 

 the space of two inches. 



The Fibula. A medullary cavity runs throughout the length of the body, reaching the 

 neck proximally, and extending to a point about 2^ inches from the distal extremity of the 

 lateral malleolus. The lateral wall of the body is usually considerably thicker than the medial. 

 The head is formed of loose spongy bone, enclosed within a very thin dense envelope. The 

 spongy tissue of the distal extremity is more compact, and acquires considerable density on the 

 surfaces underlying the articular area and the pit behind it. The canal for the nutrient artery of 

 the body opens into the medullary cavity about an inch distal to its external aperture. 



The Bones of the Foot. A longitudinal section through the articulated bones of the foot 

 reveals the fact that the structure of the spongy substance of each individual bone is determined 

 by the stress to which it is habitually subjected. In this connexion it is necessary to refer to the 

 arched arrangement of the bones of the foot, a subject which is also treated in the section which 

 deals with the Joints. The summit of the arch is formed by the talus, on which rests the tibia. 

 Subjected as the talus is to a crushing strain, it is obvious that this load must be distributed 

 throughout the arch, of which the calcaneus is the posterior pillar, whilst the heads of the meta- 

 tarsal bones constitute the anterior pillar. It is found, consequently, that the lamellae of the 

 spongy tissue of the talus are arranged in two directions, which intercross and terminate 

 below the dorsal articular surface. Of these fibres, some sweep backwards and downwards 

 towards the posterior calcanean facet, beyond which they are carried in the substance of the cal- 

 caneus in a curved and wavy manner in the direction of the heel, where they terminate ; whilst 

 others, curving downwards and forwards from the trochlea of the talus, pass through the 

 neck to reach the articular surface of the head, through which in like manner they may be 

 regarded as passing onwards through the several bones which constitute the anterior part of the 

 arch, thus accounting for the longitudinal striation as displayed in the structure of the navi- 

 cular, cuneiform, and metatarsal bones. In the calcaneus, in addition to the foregoing arrange- 

 ment, another set of curving fibres sweep from back to front of the bone beneath the more com- 

 pact tissue which forms its under shell. These are obviously of advantage to prevent the spread 

 of the bone when subjected to the crushing strain. In the sustentaculum tali a bracket-like 



