ANATOMY AND SUBDIVISION OF NERVOUS SYSTEM 115 



The cerebellum appears in the evolutionary history of the 

 vertebrate brain much earlier than the cerebral cortex; its 

 functions are wholly reflex and unconscious (see pp. 158, 186) 

 and are concerned chiefly with motor coordination, equilibra- 

 tion, and, in general, the orientation of the body and its members 

 in space. Its activities are of the invariable, innate, structurally 

 predetermined type (see pp. 22, 31, 78). The cerebral cortex, 

 on the other hand, is the organ of the highest and most plastic 

 correlations, which are in large measure individually acquired. 

 It attains its maximum size in the human brain. 



In recognition of the late phylogenetic origin of the cerebral 

 cortex Edinger has called the entire brain stem and cerebellum 

 the old brain (palaencephalon), and the cerebral cortex and 

 parts of the brain developed in relation therewith the new brain 

 (neencephalon). 



The terminology of the brain is in great confusion. Most of 

 the more obvious parts were named before their functions were 

 known, the same part often receiving many different names, and 

 sometimes the same name being applied to very different parts. 

 To remedy this situation the German Anatomical Society in 

 1895 published an official list of anatomical terms which is known 

 as the Basle Nomina Anatomica (commonly abbreviated as 

 B. N. A.). Each of these terms has a clearly denned significance 

 and they are now very widely used, though many anatomists 

 continue to use some older and unofficial names. The B. N. A. 

 terms or their English equivalents are used in this work, save in 

 a few cases which are specifically mentioned. The terminology 

 of the brain is based upon the embryological researches of Pro- 

 fessor His, and can best be outlined by reviewing the form of the 

 human brain at a few selected stages of development. 



The B. N. A. terminology was developed with exclusive reference to the 

 human body. The names of many parts of the bodies of other animals than 

 man and of microscopic structures in general are not included. The names 

 of this list are all used and defined in W. Krause's Handbuch der Anatomic 

 des Menschen, Leipzig, 1905, and in most of the recent American and 

 English text-books of anatomy. At the end of Krause's book is a very com- 

 plete list of synonyms, including most of the anatomical terms in use and 

 their B. N. A. equivalents. 



Following the example of many other recent anatomists, we shall in this 

 work replace the B. N. A. term "anterior" (on the front or belly side) by the 

 word "ventral," and the B. N. A. term "posterior" (on the back side) by 



