INTRODUCTION. 3 



and batrachians, has been already extensively studied. In the list of pub- 

 lications given farther on, it will be noticed that many of the writers have 

 taken for study one animal at a time, and it will be found also that 

 the works of most of them treat of their subjects very exhaustively. 



In the present work, no one animal is made a special object of re- 

 search ; but anatomical facts, taken from the different types, are brought 

 together in order to facilitate comparison. The presentation of some of 

 the most striking points of difference and resemblance, with a brief no- 

 tice of a few appearances and structures, which it has been my good 

 fortune to discover, form the greater part of the text. 



Others may here find for themselves useful data which have es- 

 caped my notice ; for it will be evident that the illustrations, being ana- 

 tomically correct, can, unlike many hand drawings, be studied as if they 

 were microscopic specimens. 



Following the example of nearly all other writers on the nervous 

 system of these animals, the relations and positions of parts are indica- 

 ted by terms which refer to the usual posture of a reptile with its abdom- 

 inal surface towards the earth. The "posterior roots," for instance, 

 of human anatomy, are here named : superior or upper roots, etc. 



Without wishing to discuss toponomy, I will here state that the 

 choice of nomenclature has been with me determined entirely by person- 

 al preference, and implies no want of appreciation of the merits of the 

 excellent system* recently proposed by Prof. B. G. Wilder. 



METHODS EMPLOYED. 



WITH the exception of the sections represented by Plates I. IV., 



* "Science," II, Nos. 38, 122-126, Nos. 39, 133, 138. Also "The Brain of the 

 Cat." Am. Philosoph. Soc., 1881. 



