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CHAPTER I 

 INTRODUCTION 



Foreword 



The internal anatomy of all but a few mammals has been 

 woefully neglected. Anatomists have heretofore shown a 

 strong propensity to seek out material representing the rarer 

 and more spectacular mammals and to neglect species 

 of a more generalized nature available in abundance. For 

 example, the anatomy of such curiosities as the aye-aye 

 (Cheiromys) and the marsupial mole (Chrysochloris) is far 

 better known than that of a single one of our more common 

 North American small mammals. Then too, our knowledge 

 of the systematic position of most groups and genera has 

 reached a deadlock, broadly speaking, since cranial and 

 external characters usually employed in their phylogenetic 

 arrangement are mostly well known. Additional work is 

 often productive only of a better arrangement of the species 

 and subspecies within a group or genus. Thus the emplace- 

 ment of the latter in the system may be largely artificial, 

 and such mistakes as may have occurred can be rectified 

 only after there has been secured a more thorough knowledge 

 of the gross anatomy. 



A handicap to the study of the anatomy, especially the 

 myology, of such mammals as rodents is the lack of a com- 

 prehensive text book. Even so common a laboratory sub- 

 ject as the white rat has never been thus treated. Existing 

 literature of this nature is either scattered and fragmentary 

 or so poorly illustrated that none but an experienced anato- 

 mist can work with it to proper advantage. In addition, the 

 average systematic mammalogist is loath to expend the time 

 and effort necessary to homologize his subject with the 



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