THE ANATOMY OF A BIBD 33 



Apteryx, which is, perhaps, further removed from the possibihties of 

 flight than any other bird. 



A very cm-ious muscle runs into the patagium of the wing, which 

 is that fold of skin which lies between the shoulder and the liand. 

 This muscle is called the patagial muscle. It starts from the 

 shoulder as a fleshy band, but soon ends in two long tendons : one 

 of these follows the upper margin of the patagium, and finally ends 

 in the wrist ; the other passes down over the patagium, and ends 

 below in connection with some of the muscles of the arm, and also 

 by being attached in a fan-shaped way to the skin itself. The 

 function of this muscle is to assist in the folding up of the wing 

 when it is, so to speak, put away after use. The tendons in which 

 the latter part of this muscle ends often show a most complicated 

 branching in the patagium ; they frequently offer characteristic 

 differences in different birds, and are made some use of by the 

 systematist. The bird has got a biceps to its arm just as we have. 

 It sometimes happens that this biceps gives off a muscular slip, 

 which runs into the patagium and becomes attached to the upper 

 of the two tendons of the patagial muscle. A good deal of stress is 

 laid by certain ornithologists as to whether this biceps slip is absent 

 or present. Several of the common British birds will afford material 

 to the beginner to ascertain for himself some of the chief variations 

 in these and the other muscles of the body. It will be a good 

 exercise to get a few birds, and to carefully dissect two of them, be- 

 longing to as widely different kinds as possible, side by side. You 

 might select, for instance, a Crow and a Pigeon, which are fairly 

 extreme types. To revert to our account of the muscular anatomy 

 of a bird, it will be impossible to attempt any comprehensive account 

 of this branch of the subject, because the facts are so appallingly 

 numerous. We shall content ourselves, therefore, with the men- 

 tion of a highly characteristic bird muscle which occurs in the leg. 

 This muscle is known as the ambiens. This muscle is thin and 

 ribbon-like. It takes its origin from a little process of the pubic 

 bone usually called the prepubic process. From this point it runs 

 along the inside of the thigh until it reaches the knee ; it then bends 

 over the knee and comes out on the other side, where it runs down 

 the leg to join the deep flexor muscle of the foot. When this 

 ambiens muscle contracts it pulls upon the flexor muscle, already 

 referred to ; the effect of this is that the toes are brought together 

 by the tendons in which the last-mentioned muscle ends. The 

 ambiens is far from being universally present among birds. It is 



