SKELETON. 383 



muscular attachment; therefore there is produced but little lateral 

 motion. This position and formation of the ilium with respect to the 

 thigh-bone is remarkable in the bird. 



The reason for the great difference between the shape of the pelvis 

 in man and other animals, is to give a circular sweep of origin to the 

 muscles of the human thigh-bones ; the pelvis being adapted to this 

 purpose by the circular spreading position of the iliac bones, making 

 a cone, the base of which expands over the thigh-bones. The aceta- 

 bulum is to be considered as the apex : it is placed laterally, looking 

 downwards and outwards, and gives a free scope to the motions of the 

 thigh-bone. This position of the bone obliges the thigh-bone to be of 

 a peculiar shape ; at first it comes out nearly in the direction of the 

 cone, forming what is called ' head ' and * neck ;' it then bends down so 

 as to give the legs a proper position for the support of the body. 



This position of the head and neck gives principally a rotatory 

 motion, upwards and downwards, which brings the body of the bone 

 outwards and inwards ; so that the rotatory motion of the head and 

 neck, joined with the up and down motion, produces the conoid motion 

 in the body of the bone. 



The body of the thigh-bone makes with the neck an angle of 56°. 

 This angle confines in some degree the motion of the thigh ; for, on 

 account of it, the body of the bone has not the quantity of motion that 

 the neck has ; or would have, if the neck were continued out in a 

 straight line from the body. 



The perpendicular column of the leg of a fowl is thrown under the 

 centre of gravity [by the forward bend of the femur]. For, although 

 the joint of the thigh is not, that of the knees is, under the centre. The 

 thigh-bone is supported in that oblique position by muscles. 



The scapula and clavicle generally move together ; but sometimes the 

 scapula moves without the clavicle. When both move together, they 

 may be compared to a pair of compasses. 



The motion of the wrist is chiefly flexion and extension : the flexion 

 is between the radius and first row of the bones of the carpus ; the ex- 

 tension is between the first and second. 



The metacarpus is to be considered as the first set of bones ; for they 

 make the basis for the others to bend upon. The second set of bones, 

 or first row of the fingers, becomes the basis of the other two ; and the 

 second row of bones of the fingers becomes the basis of the last of all. 

 In proportion as these bones become shorter, they describe, in their 

 movements, the section of a smaller circle. The tails of some animals 

 are constructed upon this principle. 



Of Ligaments. — Ligaments are parts commonly composed of strong 



