PREFACE 



In one of the frescoes of the Sistine Chapel, Michelangelo portrays 

 Adam after his creation by Jahveh. The frontispiece of this book shows 

 only enough of this painting to suggest that Jahveh had a hand in the 

 event; but how Jahveh accomplished his creative work is left to biologists 

 who have tried to solve by scientific methods the problem of the genesis 

 of the human body. Such scientific investigation is not concerned with 

 the question of the ultimate origin of the universe nor of the presence or 

 absence of God in the cosmos, but with the secondary factors which 

 determine physical events in the physical world. 



The scientific evidence which bears upon the problem of the genesis of 

 the human body is derived chiefly from the sciences of paleontology, 

 comparative anatomy, and embryology. These sciences provide the 

 factual support of the evolution theory, which in turn furnishes the clue 

 to the origin of species, including the human species. The remarkable 

 development of these sciences since Darwin's day may be attributed to 

 the conviction of biologists that by means of them light may be thrown 

 on the history of organisms in general and of the human body in particular. 

 Today such courses form standard constituents of the biological curricula 

 of universities and colleges. 



American undergraduates study comparative anatomy not so much 

 from interest in lower animals as to gain the best approach to an under- 

 standing of human structure and function. The details of comparative 

 anatomy in themselves interest the average undergraduate slightly if at 

 all. To elicit the attention of the student the facts must be interpreted 

 for him and given meaning in terms of function or of genetic relations. 

 The earlier books in comparative anatomy served better as works of 

 reference than as college texts. The multiplicity of facts presented in 

 them tended to confuse the student, who consequently was unable to see 

 the woods for the trees. 



The facts presented in this book have been selected chiefly because 

 they throw light upon the important problem of man's place in nature and 

 because they help the student to understand the major functions of his 

 body. If greater stress is laid upon morphological than upon physiological 

 matters, this is done, not because students are more interested in morpho- 

 logical problems, but because the authors are convinced that the central 

 problem of life is that of form. The best approach to this problem is 

 through the study of the changes which the body undergoes in ontogenesis 

 and phylogenesis. College and medical courses in physiology usually 

 assume that the student has a basis for them in a knowledge of the facts of 

 anatomy. 



