Preface vii 



adult anatomy cannot be fully intelligible without knowledge of de- 

 velopmental processes. Should a chapter (or chapters) on embryology 

 precede or follow the description of adult structure? In either order, 

 more or less of the cart is put before the horse. The second problem is 

 offered by the classification of animals. Classification is based chiefly on 

 comparative anatomy and embryology. Therefore logically the classifi- 

 cation should follow the descriptive chapters. But anatomic compari- 

 sons necessitate mention of numerous animals, many of which are quite 

 unknown to most readers. Identification of these animals to the reader 

 is greatly facilitated if the anatomic description is preceded by a classi- 

 fication in which groups are defined and representative animals are 

 mentioned. Again, neither arrangement puts cart and horse in good 

 working order. 



Mere knowledge of facts has little value. It acquires value only 

 when it is accompanied by such understanding as enables its possessor 

 to act to greater advantage than he otherwise could ; or when apprecia- 

 tion and interpretation of facts broaden the intellectual horizon and 

 give the individual the satisfaction of feeling that his world is expand- 

 ing. Appropriate knowledge of anatomy enables a surgeon to perform 

 a successful appendectomy. But he who possesses appreciation of the 

 significance of the facts of comparative morphology and paleontology 

 finds himself standing on a crest of Time whence he may look back- 

 ward down a vista of hundreds of millions of years and behold a vast 

 procession of successively dominant groups of animals. In this succes- 

 sion he discovers certain trends which appear as if progressively directed. 

 Knowing that present is but a shifting point in a continuity which is 

 always past and future, and recognizing these trends in the past, he 

 may then turn his eyes toward the future and gain some preview, 

 admittedly dim and misty, of the destiny of his own race. If he is 

 intelligent, as he claims to be, this preview should be a determining 

 factor in his present behavior. 



The foregoing paragraphs of this preface set forth the considerations 

 which led the author of "The Chordates" to undertake a book which, 

 to its content of anatomic fact, should add chapters (necessarily brief) 

 giving the reader some knowledge of the history of anatomic science, 

 the ideas and motives which have directed its progress through succes- 

 sive centuries, the theories and principles whereby it has worked, and, 

 above all, an appreciation of its vital human import. The inclusion of 

 such chapters in a book of necessarily limited size must be at the ex- 

 pense of its content of anatomic fact. This is to be justified on the 

 ground that an appreciative knowledge of the more basic facts of 

 comparative morphology is of greater value (except for some technical 

 purposes) than a more detailed factual knowledge without the apprecia- 



