Editorial, Prohloi/s of Co7)iparativc Neurology. 95 



foundation for the analytic study of the brain from tlie com- 

 parative standpoint. 



It has so often happened that just the chie necessary for 

 the explanation of a complicated nervous structure has been 

 found in the simpler homologue in a lower type, that it 

 seems strange that the comparative method has been so fre- 

 quently neglected, and especially that embryology has been 

 so little employed in the investigation of the more compli- 

 cated organs. Nevertheless, since the publication of the 

 exhaustive w^ork by Mihalkovics on the " Development of 

 the Vertebrate Brain," a great deal has been contributed to 

 our knowledge of the archetectonic of the nervous system by 

 embryology. 



To a very large extent, effort has been concentrated of 

 late upo-n histological investigation, and, as usual, the pri- 

 mary impetus has been given by improvements in technique 

 which make accessible to any one structures which from 

 their delicacy and minuteness had hitherto been regarded as 

 beyond the reach of observation. These refinements in 

 technique have also had the effect of undermining several of 

 the most substantial generalizations of an earlier decade. 



The methods which have excited most interest, and from 

 which much is expected, if not already obtained, are the 

 various forms of metallic impregnation introduced by Golgi, 

 elaborated by Cajal and adopted by Kolliker. While all of 

 these methods are more or less fickle and open to the objec- 

 tion that they emphasize one element in the structure with- 

 out affecting the others, and do not with certainty differen- 

 tiate nervous from non-nervous structures, yet in careful 

 hands the results can but prove very suggestive. The 

 following brief summary may serve at once to show what 

 has been done and to indicate the paths by which greater 

 attainment may be reached. 



It is to-day an unquestioned dictum of biology that func- 

 tion and structure are intimately connected, and that differ- 

 ence in function implies difference in structure. Yet in the 



