V. 



The Value of Myology as an Aid in the 

 Classification of Animals.' 



THE opinion of most systematists, and of anatomists too, is, I 

 believe, that the study of muscles is not of much value for 

 classificatory purposes ; first, because muscles are liable to a good 

 deal of individual variation ; secondly, because they are often difficult 

 to identify by those who are not specially working at them ; and 

 thirdly, because of the impression that the arrangement of the 

 muscles depends largely on the habits and mode of life of the animal 

 to which they belong. 



With regard to the first objection, that muscles are very variable, 

 Dobson in 1884^ stated his opinion that the muscles of the lower wild 

 mammals do not show anything like the same proportion of abnor- 

 malities that are met with in man. This opinion my own experience 

 bears out, although I am bound to confess that variations do occur 

 fairly often. Still, if several muscles are taken, the risk of any serious 

 inconvenience from this source is small. 



The second objection is not a very serious one. Nobody wishes 

 to lay any stress on slight differences of size or attachment, but rather 

 on the presence or absence of muscles, and on the shifting of their 

 attachments from one bone to another. 



The third question, namely, the extent to which muscles vary 

 with the mode of life of their possessor, is the one which I wish to 

 consider most fully. I propose to put forward certain facts gathered 

 from a study of the muscles of the great Order, Rodentia, an Order 

 which contains climbing, swimming, digging, running, and, in a sense, 

 flying forms. Thus I hope to substantiate my contention, that the 

 muscles of an animal tell much more about its classificatory position 

 and the habits of its ancestors than about its own present habits. 



One of the most interesting points in the myology of rodents has 

 already been discussed by Dobsons ; it is the relation which the two 

 long flexors of the sole bear one to the other. These two flexors are 

 spoken of in human anatomy as the " flexor longus hallucis," which 



1 Paper read before Section D of the British Association, Ipswich, 1895. 

 ^Jouin. Anat., xix,, p. i6. " Journ. Anat., xvii., p. 142. 



