THE MUSCLES OF THE UPPER EXTREMITY. 109 



iii many of our American Hawks and Owls (Bull. 

 Nutt. Oniitho. Club, vol. vi. No. 4, October, 1881). I 

 also showed how among these latter birds, when the 

 wing was extended the tendon of the tensor patagii 

 long us raised the os prominens, and thereby increased 

 the extent of the alar superficies (loc. cit., p. 200). 

 In foregoing paragraphs of the present work, I have 

 already described the dermo-tensor patagii muscle, 

 and how it acts as an auxiliary to the tensor patagii 

 longus. 



Before entering upon our detailed descriptions of the 

 tensor patagii muscles, I desire to say a word here as to 

 how they are best studied in general. This I do from 

 the fact that in the future there will no doubt be many 

 dissections made of these muscles, as they have been 

 proven to be of no little classificatory value in birds, as 

 I have already remarked. 



First, it may be as well to add, that in certain birds 

 another small muscle occurs in this region ; it has been de- 

 scribed as the bicipital slip to thepatogium (Figs. 35 bis 

 and 35 ter, B. slip}. This is a fleshy fasciculus of muscle 

 that is differentiated off from the anterior surface of 

 the biceps, and passing between the cutaneous folds 

 of the patagium becomes inserted into the tendon of 

 the tensor patagii longus at about the middle of its 

 course. 



Garrod states that " the presence or absence of this 

 muscular fasciculus is a very constant character among 

 closely allied birds." He not only found it in the Capri- 

 mulgi, but also in Plovers, Cranes, Gulls, Auks, and 

 some few other groups. It is absent in the Corvidcs. In 

 Fig. 35 ter, I present its appearance as it occurs in our 

 Mourning Dove, a bird I especially dissected to show it 

 as an illustration in the present connection. 



