VARIATIONS IN THE SKELETON. 281 



Hip Bone. Some of the anomalies met with in the hip bone are due to ossification of the 

 ligaments connected with it ; in other cases they depend on. errors of development. Failure 

 of union between the pubic and ischial rami has also been recorded. Cases have occurred where 

 the obturator groove has been bridged across by bone, and one case is noted of absence of the 

 acetabular notch on the acetabular margin. In. rare cases the os acetabuli (see Ossification) 

 remains as a separate bone. Berry (Journ. Anat. and Physiol. vol. xlv. p. 202) has drawn attention 

 to the occurrence of a small accessory articular facet, situated on the rough non-articular area im- 

 mediately behind the auricular surface of the ilium, which articulates with a depressed facet on the 

 posterior surface of the sacrum to the lateral side of the first posterior sacral foramen, in the neigh- 

 bourhood of the transverse process of the second sacral segment. This he homologises with the 

 normal articulation between the ilium and sacral transverse processes found in many lower animals. 



Femur. Absence of the fovea on the head of the femur for the attachment of the liga- 

 mentum teres has been recorded. This corresponds with the condition met with in the orang. 

 Not infrequently there is an extension of the articular surface of the head on to the anterior and 

 upper aspect of the neck ; this is a " pressure facet " caused by the contact of the iliac portion 

 of the acetabular margin with the neck of the bone, when the limb is maintained for long periods 

 in the flexed position, as in tailors, and also in those races who habitually squat (Lane, Journ. 

 Anat. and Physiol. vol. xxii. p. 606). 



The occurrence of a trochanter tertius has been already referred to. Its presence is not 

 confined to individuals of powerful physique, but may occur in those of slender build, so far 

 suggesting that it is not to be regarded merely as an indication of excessive muscular develop- 

 ment. The observations of Dixon (Journ. Anat. and Physiol. voL xxx. p. 502), who noted the 

 occurrence of a separate epiphysis in three cases in connexion with it, seem to point to its 

 possessing some morphological significance. Occasionally the gluteal tuberosity may be replaced 

 by a hollow, the fossa hypotrochanterica, or in some cases the two may co-exist. 



The angle of the neck is more open in the child than in the adult, and tends to be less 

 when the femoral length is short and the pelvic width great conditions which particularly 

 appertain to the female. There is no evidence to show that after growth is completed any 

 alteration takes place in the angle with advancing years (Humphry). 



The curvature of the body may undergo considerable variations, and the appearance of the 

 posterior surface of the bone may be modified by an absence of the linea aspera, a condition 

 resembling that seen in apes ; or by an unusual elevation of the bone which supports the ridge 

 (femur a pilastre), produced, as Manouvrier has suggested, by the excessive development of the 

 muscles here attached. 



Under the term " platymerie" Manouvrier describes an antero-posterior compression of the 

 proximal part of the body, frequently met with in the femora of prehistoric races. 



Patella. Cases of congenital absence of the patella have been recorded. 



F. C. Kempson (Journ. Anat. and Physiol. vol. xxxvi.) has recently drawn attention to the 

 condition described as emargiiiation of the patella. In specimens displaying this appearance the 

 margin of the bones is concave from a point about half an inch to the lateral side of the middle 

 line, to a point half-way down the lateral margin of the bone ; here there is usually a pointed 

 spine directed proximally and laterally. The condition appears to be associated with the insertion 

 of the tendon of the vastus lateralis. G. Joachimstal (Archiv u. Atlas der normalen und patholo- 

 gischen Anatomie in typischen R&ntgenbildern, Bd. 8) figures a case in which on both sides the 

 patella was double in an adult, the distal and much the smaller portion was embedded in the 

 ligamentum patellae. 



Tibia. The tibia is often unduly compressed from side to side, leading to an increase in its 

 antero-posterior diameter as compared with its transverse width. This condition is more 

 commonly met with in the bones of prehistoric and savage races than in modern Europeans. 

 Attention was first directed to this particular form by Busk, who named the condition 

 platyknemia. The general appearance of such tibiae resembles that seen in the apes, and 

 depends on an exceptional development of the tibialis posterior muscle, though, as Manouvrier 

 has pointed out, in apes this is associated with the direct action of the muscle on the foot, as in 

 climbing, whereas in man, as a consequence of the bipedal mode of progression, the muscle is 

 employed in an inverse sense, viz., by steadying the tibia on the foot, and thus providing a fixed 

 base on which the femur can move. This explanation, however, is disputed by Derry (Journ. 

 Anat. and Phys. vol. xli. p. 123). Such platyknemic tibiae are occasionally met with in the 

 more highly civilised races, and are, according to Manouvrier, associated with habits of great 

 activity among the inhabitants of rough and mountainous districts. 



Another interesting condition is one in which the proximal extremity is more strongly recurved 

 than is usual. This retroversion of the head of the tibia was at one time supposed to represent 

 an intermediate condition in which the knee could not be fully extended so as to bring the axis 

 of the leg in line with the thigh ; but such opinion has now been upset by the researches of 

 Manouvrier, who claims that it is the outcome of a habit not uncommon amongst peasants and 

 countrymen, viz., that of walking habitually with the knees slightly bent. 



Habitual posture also leaves its impress on the form of the tibia, and in races m which the 

 use of the chair is unknown, the extreme degree of flexion of the knee and ankle necessitated by 

 the adoption of the squatting position as an attitude of habitual rest is associated with an increase 

 in the convexity of the lateral condylic surface, and the appearance, not infrequently, of a 

 pressure facet on the anterior border of the distal extremity, which rests in that position on the 

 neck of the talus. Cases of congenital absence of the tibia have been frequently described, 

 amongst the most recent being those recorded by Glutton, Joachimsthal, Bland-Sutton, and Waitz. 



