Herrick, Brain of Certain Reptiles. 137 



to stand a rigid test in detail for such a purpose. A compari- 

 son of the structure of Anura and Urodeles must always take 

 this into account. 



5. In spite of these great differences and allowing for the 

 practical absence of the cerebellum in Urodela there is remark- 

 able correspondence not only with each other but with Reptilia 

 in the actual fibre-connections. 



6. The study of the fish brain is a good preparation for 

 making out the amphibian problem. 



7. The "projection system" theory of Meynert should 

 be expanded. A more general theory of Jicnral eoncatenaticm 

 (no simpler term suggests itself) is nearer the truth. Chains of 

 nervous translation may be affected between appropriate centres 

 by the intercalation of as many neurons as may be necessary. 

 There is no necessity for a physical continuum but a series of 

 reciprocating elements is sufficient. The last stage in such a 

 transformation is a perfect nerve fibre with shunted nuclei and 

 continuous fibre. This is an expedient for rapid transit over 

 long distances. The first stage in the series may be a slight re- 

 ciprocal influence of parallel neurons through their processes. 

 (See article page 1 1 of this volume.) 



8. A physiological concomitant of this anatomical theory 

 is that of zygonwrphisni which may be succinctly defined as the 

 theory that when adjacent elements are brought into relations of 

 mutual influence or one becomes a discharging agent for the 

 other there is a tendency for the cells concerned to adjust them- 

 selves to each other. At first the result is interstitial change, 

 later a closer connection is affected, and, still later, a polarity or 

 actual rearrangement of the cell axes and, finally, a fusion and 

 insulation may be developed by the transferring of the influence 

 of the nuclei to the periphery and a change in the nutritive pro- 

 cesses of the latter. 



9. So far as our histological results are concerned we must 

 confess their incompleteness but trust that enough has been 

 suggested to indicate that the same structures (however obscured) 

 exist in the frog as in higher vertebrates and that the gray mat- 

 ter is by no means so homogeneous as usually regarded. The 



