IV PREFACE. 



material has been collected which is published here for the first 

 time. The new observations, which are found in nearly every 

 chapter, have to do chiefly with the brains of selachians, ganoids 

 and amphibians, and with the origin of the organs of the sense of 

 taste. The whole discussion of the phylogeny of the forebrain 

 in chapter XVIII may be regarded as a new contribution to the 

 subject, since the account given differs in essential respects from 

 the earlier views of the author and from those of other writers. 

 The proof that taste buds have their origin in the entodermal 

 lining of the pharynx establishes an exception to the statement 

 that all nervous structures are derived from ectoderm. It sug- 

 gests the further possibility that some of the peripheral plexuses 

 of the sympathetic system may form a second exception. 



The nomenclature of the nervous system is in a very unsatis- 

 factory state for want of a guiding principle. It is believed that 

 a guiding principle is furnished by the mode of treatment here 

 attempted. The usual description of the nervous system based 

 upon mere structural relations is quite lacking in life and meaning, 

 and no set of terms has any commanding force. Significance 

 and essential fitness of terms can come only with the study of the 

 nervous system from the point of view of functional relationships. 

 It is not yet time for a general revision of nomenclature on this 

 basis. Accordingly the BNA terms which are now the most 

 generally familiar, have been employed as far as they are adequate. 

 The few new terms that have been introduced are necessary for 

 the description of the functional divisions of the nervous system. 

 InTdescribing brain tracts compound names have been employed 

 which indicate the origin and ending of the constituent fibers. 

 Care has been taken to use as the first part of the compound name 

 the name of the nucleus of origin of the fibers. For the sake of 

 consistency and clearness it is necessary to put the names of most 

 nerve centers and tracts into the Latin form. In many places, 

 however, English equivalents have been used interchangeably 

 with the Latin terms. The object has been to deviate as little as 

 may be from common language in a subject in which technical 

 terms must be so largely used. 



The majority of the illustrations are made from original draw- 



