24 ANATOMY OF THE WOOD RAT 



same. There are minute differences that may be, and 

 undoubtedly are, phylogenetic in character; there are 

 analogous, ontogenetic differences caused by the fact 

 that the life led by various individuals causes variation 

 in the muscular development ; and finally, no two specimens 

 ever ''set" in precisely the same position after having 

 been placed in preservative. 



It should also be noted that in many instances it is 

 impossible to define the exact bounds of the attachment of 

 a muscle. This is especially the case when a muscle ends 

 in fascia. In addition, difficulties in deciding whether or 

 not certain differences are relative are presented when an 

 unusually large Teonoma is compared with a subadult 

 Neotoma of much smaller size. 



Myological terminology is in a fairly satisfactory state 

 of standardization as regards human anatomy, but this is 

 far from so in the case of the lower mammals. Hence, until 

 an authoritative revision of the nomenclature with special 

 reference to the lower Mammalia has been made, no stand- 

 ard can be attained. Many of the usual muscle names 

 are misleading when applied to such a manamal as the 

 wood rat, but the coining of new terms by the individual 

 investigator is to be deplored, and the only practical course 

 to follow in most cases seems to be the employment of such 

 names, established by usage, as appear best to fit the sub- 

 ject in hand. 



MUSCLES OF THE HEAD 



The muscles of the head are treated under the following 

 headings: 



Superficial facial musculature 

 Masticatory musculature 

 Interramal musculature 

 Muscles of the tongue 



