PREFACE 



Comparative anatomy has both practical and theoretical interest. 

 Courses in it based, like other science courses, upon laboratory work give 

 the student first-hand acquaintance with the structure of fishes, amphi- 

 bians, reptiles, birds and mammals. If, as psychologists assert, all our 

 ideas derive from sense impressions, all real knowledge of animal structure 

 must be based upon such laboratory experience. "Starve the senses and 

 you starve the soul." In the laboratory, as the student increases his 

 acquaintance with animals, he gains also in resourcefulness and inde- 

 pendence. Many biologists believe that comparative anatomy affords 

 the best approach to the understanding of human structure and function. 

 In many American colleges and universities the course in comparative 

 anatomy is a prerequisite to advanced courses in histology, embryology 

 and physiology. In this way the student passes in his analysis from the 

 general to the particular, from the gross to the microscopic. 



To many persons, however, the theoretical interest of comparative 

 anatomy makes stronger appeal than does practical familiarity with 

 animals. The major problem which faces the student of comparative 

 anatomy is that of the genesis of the human body. The clue which 

 gives meaning to many of the details of anatomy is found in the evolution 

 theory. Most teachers of biology are so convinced of the truth of that 

 theory that the issue is no longer debated by them. Each generation, 

 however, must examine for itself the evidence which has led to the general 

 acceptance of evolution by experts. While the record of the rocks is 

 probably the most convincing evidence of evolution, the facts of com- 

 parative anatomy greatly strengthen the case for evolution. As a result 

 of the researches of several generations of comparative anatomists, it is 

 now possible to sketch in fairly firm outlines the hypothetical past history 

 of the human body. One of the purposes of this book is to summarize 

 some of this evidence. 



To meet the laboratory needs of students, a number of excellent labora- 

 tory guides have been written, some dealing with the dissection of a 

 single animal, others with several animals. Most of them, however, make 

 no attempt to deal with animals comparatively. They let the student 

 make his own comparisons, which is possibly more than may be expected 

 of him. The present book is intended to help him in these comparisons 

 and to correlate and interpret the facts gathered in the laboratory. The 



