SALAMANDERS AND THEIR BRAINS 9 



cochlear rudiment and its nerve appear in the frog, the tissue of the 

 "dorsal island" receives the cochlear nerve with radical change in the 

 functions performed (p. 138). 



The histological texture of these brains is so different from that of 

 mammalian brains that the development of an intelligible nomencla- 

 ture presents almost insuperable difficulty — a difficulty exacerbated 

 by the fact that in the early stages of the inquiry it was necessary to 

 apply descriptive terms to visible structures before their relation- 

 ships were known. With increase of knowledge, errors were corrected, 

 and unsuitable names were discarded; but terms already in use are 

 still employed so far as possible, even though they are in some cases 

 cumbersome and now known to be inappropriate. In all these descrip- 

 tions I have consistently used the word "fissure" to designate visible 

 furrows on the external surface of the brain and "sulcus" for those on 

 ventricular surfaces. Attention is called to the list of abbreviations 

 (p. 391) and to previous lists there cited where synonyms are given. 

 In all my published figures of brains of urodeles the intent has been 

 to use the same abbreviations for comparable structures. This inten- 

 tion has been approximately realized, but there are some incon- 

 sistencies, in most of which the differences express a change in em- 

 phasis rather than a correction of errors of observation. 



Many well-defined tracts of fibers seen in fishes and higher animals 

 are here represented in mixed collections of fibers of diverse sorts, 

 here termed "fasciculi," or they may be dispersed within a mixed 

 neuropil. The practice here is to define as a "tract" all fibers of like 

 origin or termination, whether or not they are segregated in separate 

 bundles. The customary self-explanatory binomial terminology is 

 used wherever practicable — a compound word with origin and ter- 

 mination separated by a hyphen. But, since a single fiber of a tract 

 may have collateral connections along its entire length, the fully 

 descriptive name may become unduly cumbersome ('41a, p. 491). 

 Thus, in accordance with strict application of the binomial ter- 

 minology, tractus strio-tegmentalis would become tractus strio- 

 thalamicus et peduncularis et tegmentalis dorsalis, isthmi et trige- 

 mini. The chemists seem to be able to manipulate similar enormities 

 even without benefit of hyphens or spaces, but not many anatomists 

 are so hardy. Few of the named tracts are sharply delimited, and all 

 of them are mixtures of fibers with different connections. Any 

 analysis is necessarily somewhat arbitrary. 



Simple action systems of total-pattern type, wherever found 





2j;. LIBRARY] 



