vi PREFACE 



some cases, no doubt, I have been unaware of the exceptions; in others I have 

 knowingly omitted them on the grounds that statements of exceptions are more 

 confusing than informative to the beginner. 



To avoid confusion the explanatory matter is printed in slightly smaller 

 type than the directions for the dissections. 



I have included in the manual such materials as seemed to me to bear most 

 directly on the story of the evolution of the various systems. I have treated 

 the skeleton and the coelom at greater length than is commonly the case. The 

 prevailing neglect of the study of the skeleton in courses in vertebrate anatomy 

 seems to me unjustifiable in view of the importance of this system in the study of 

 phylogenetic and evolutionary questions. It is true that skeletal material is 

 somewhat expensive to purchase and maintain, but a good many of the more 

 important materials can be prepared by the instructor or students. In presenting 

 the vertebral column I have adopted Gadow's conception of the development 

 of the vertebrae from separate arcualia, an idea also adopted by Schauinsland in 

 his account of the development of the vertebrae in Hertwig's Handbuch. The 

 conception would appear to be correct in the main, and at least furnishes a simple 

 explanation for the variety of vertebral columns encountered among vertebrates. 

 The difficulties attending the study of the coelom and mesenteries do not seem 

 to me to justify one in disregarding them. I hope the simplified account I have 

 presented after long study and thought on the matter will aid in the understand- 

 ing of this complex subject. As to the animals to be dissected, the elasmobranch 

 must naturally form the point of departure in the study of comparative anatomy. 

 I have described the skate in addition to the dogfish, since some teachers prefer 

 it; it is certainly more favorable than the dogfish for the study of the nervous 

 and urogenital systems, but less favorable, in my opinion, for the study of the 

 circulation. The not infrequent scarcity of dogfish in recent years makes it 

 desirable that an alternative form be described. The bony fish is omitted because 

 its specialized structure would confuse rather than aid the student in following 

 out the evolution of the systems. The frog is so often used in general and begin- 

 ning courses that it seems superfluous to consider it here. Further, the urodeles 

 serve our purpose much better. I should like to have included Cryptobranchus 

 as alternative to Necturus, but the limits of space forbade. The reptile is impor- 

 tant for the purposes of a comparative course, and the turtle is perhaps the most 

 readily obtainable form of sufficient size. The bird has been included since it 

 seemed inadvisable to omit altogether an entire vertebrate class. I have de- 

 scribed both the cat and rabbit, as the former animal, though perhaps preferable 

 in some respects, is not always readily obtainable. 



At the University of Chicago the course consists of a brief glance at the 

 external features of the lower chordates and of representative vertebrates; of all of 

 the work given in the manual on the exoskeleton, endoskeleton, and muscles, 

 with the exception of the muscles of Necturus; and of the complete dissection 



