776 REPORT— 1897. 



front is greater than the average pull, per unit of length, of the muscles attached 

 behind in the same region. 



The muscles which lie on the back of the neck and which are attached to the 

 occipital part of the skull, when brought into action, will necessarily affect 

 the position of the head. The new-born infant has no power to raise the head, 

 which is bent forward, so that the chin is approximated to the chest. As it 

 acquires strength the head becomes raised by the muscles of the back of the neck, 

 and the flexible spine in the cervical region loses its primary curve, concave 

 forwards, and gradually assumes the cervical convexity. The formation of this 

 curve is, I believe, assisted by the anterior recti muscles, the lower ends of which 

 are attached to the front of the vertebrae, whilst their upper ends are connected to 

 the basi-occipital. In the elevation of the head the opposite ends of the muscles 

 are drawn apart, which would exercise a forward traction upon the cervical 

 vertebrae. The production of the cervical convexity precedes the formation of the 

 lumbar curve, for an infant can raise its head, and take notice of surrounding 

 objects, months before it can stand upon its feet. 



We shall now look at the bones in the thigh and leg, which possess characters 

 that are distinctively human, and which are associated with the erect posture. 

 These characters can be more clearly recognised when the bones are contrasted 

 with the corresponding bones of the large Anthropoid apes. 



As compared with the ape, the shaft of the human thigh bone is not so broad 

 in relation to its length ; when standing erect the shaft is somewhat more oblique, 

 it is more convex forwards and generally more finely modelled, and it has three 

 almost equal surfaces, the anterior of which is convex. But, further, a strong ridge 

 (linea aspera) extends vertically down its posterior surface ; so that a section 

 through the shaft is triangular, with the two anterior angles rounded and the 

 posterior prominent. In the Gorilla, Chimpanzee, and Orang, the shaft is flattened 

 from before backwards, and the linea aspera is represented by two faint lines, 

 separated from each other by an intermediate narrow area. A section through the 

 shaft approximates to an ellipse. In the Gibbon the femur is greatly elongated, 

 and the shaft is smooth and cylindriform. The linea aspera is for the attachment 

 of powerful muscles, which are more closely aggregated in man than in apes, so 

 that the human thigh possesses more graceful contours. 



In the human femur the shaft is separated from the neck by a strong anterior 

 intertrochanteric ridge, to which is attached the ilio-femoral ligament of the hip 

 joint, which, by its strength and tension, plays so important a part in keeping the 

 joint extended when the hody is erect. In the Anthropoid apes this ridge is faint 

 in the Gorilla, and scarcely recognisable in the Orang, Gibbon, and Chimpanzee, and 

 the ilio-femoral ligament in them is comparatively feeble. It may safely therefore 

 be inferred that in apes, with their semi-erect, crouching attitude, the ilio-femoral 

 band is not subjected to, or capable of sustaining, the same strain as in man. 



The head of the thigh bone is also distinctive. In the apes the surface covered 

 by cartilage is approximately a sphere, and is considerably more than a hemi- 

 sphere. It is sharply difierentiated from the neck by a definite boundary, and it 

 has a mushroom-like shape. In man the major part of the head is also approxi- 

 mately a sphere ; but, in addition, there is an extension outwards of the articular 

 area on the anterior surface and upper border of the neck of the bone. The form 

 of this extended area differs from the spherical shape of the head in general. The 

 curvature of a normal section of its surface has a much larger radius than the 

 curvature of a normal section of the head, near the attachment of the ligamentum 

 teres. 



The amount of this extended area varies in diflferent femora, but as a rule it 

 is larger and more strongly marked in Europeans than in the femora of some 

 savages which I have examined. When the joint is in the erect attitude, the 

 area is in contact with the back of the iliac part of the iho-femoral ligament. It 

 provides a cartilaginous surface which, during extension of the joint, is not situated 

 in the acetabulum, but, owing to the centre of gravity falling behind the axis of 

 movement, is pressed against that ligament, and contributes materially to its 

 tension. It is associated with the characteristic position of the human hip joint in 



