4 THE BRAIN OF THE TIGER SALAMANDER 



Zoological names. — The approved names of the genus and larger groups to which 

 reference is here made, as given in a recent official list (Pearse, '36), are as follows: 



Salienta, to replace Anura 



Caudata, to replace Urodela 



Ambystoma, to replace Amblystoma 

 Amby stoma (or Siredon) maculatum has priority over A. punctatum. The names, 

 Anura, Urodela, and Amblystoma, are used throughout this text because they are 

 so commonly found in current literature that they may be regarded as vernacular 

 terms. 



THE SCOPE OF THIS INQUIRY 



From the dawn of interest in the minute structure of the human 

 brain, it was recognized that the simpler brains of lower vertebrates 

 present the fundamental features of the human brain without the 

 numberless complications which obscure these fundamentals in 

 higher animals. This idea motivated much research by the pioneers 

 in neuroanatomy, and it was pursued systematically by L. Edinger, 

 H. Obersteiner, Ramon y Cajal, C. L. Herrick, J. B. Johnston, 

 Ariens Kappers, and many others. In 1895, van Gehuchten wrote 

 that he was engaged upon a monograph on the nervous system of the 

 trout, "impressed by the idea that complete information about the 

 internal organization of the central nervous system of a lower verte- 

 brate would be of great assistance as our guide through the compli- 

 cated structure of the central nervous system of mammals and of 

 man." The few chapters of this monograph which appeared before 

 his untimely death intensify our regret that he was not permitted to 

 complete this work. Van Gehuchten's ideal has been my own in- 

 spiration. 



Our primary interest in this inquiry is in the origins of the struc- 

 tural features and physiological capacities of the human brain and 

 the general principles in accordance with which these have been de- 

 veloped in the course of vertebrate evolution. This is a large under- 

 taking. What, then, is the most promising approach to it.'^ My 

 original plan was, first, to review all that has been recorded about the 

 anatomy and physiology of the nervous systems of backboned ani- 

 mals, to arrange these animals in the order of their probable diverse 

 specialization from simple to complex in the evolutionary sequence, 

 then to select from the series the most instructive types and subject 

 them to intensive study, in the expectation that the principles under- 

 lying these morphological changes would emerge. 



So ambitious a plan, however, is far too big to be encompassed 

 within the span of one man's lifetime. The fact-finding research is 



