Thompson, Medullation of Cottical Fibers. 359 



comparing brains of abnormal individuals with those of normal 

 individuals ; and, 3) it opens the way to an important advance 

 in comparative anatomy — the comparison of intra-cortical fiber 

 structure throughout the vertebrate series. The material exam- 

 ined by Kaes with a view to the solution of his problem com- 

 prises eleven human brains. Seven of them were those of 

 normal individuals belonging to the laboring class of the Ger- 

 man race. Their ages were ij^ ; 18 ; 38 ; 42 ; 45 ; 45 ; and 

 53 years. Two of the four remaining brains were those of 

 Asiatic seamen, one a Chinaman and one a Hindu, each about 

 forty years of age. The remaining two brains were abnormal — 

 one that of an idiotic dwarf, 25 years of age ; and the other that 

 of a microcephalic child of 2^^ years. 



The brains were all prepared according to the same general 

 method.^ They were divided into twelve frontal sections and 

 cubical pieces of cortex were taken at various points from each 

 section. These pieces of cortex were prepared according to 

 Wolter's method ^ — a method which stains the medullated fibers 

 gray or black, leaving the other cortical substance yellow. 



Two general methods of examining the sections were pur- 

 sued, one macroscopic and the other microscopic. The macro- 

 scopic method consisted in noting the prevailing color of each 

 section. Since in the stain used the medullated fibers appear 

 gray and all other substance yellow a region which is very 

 rich in medullated fibers appears a uniform gray ; while one 

 that is entirely lacking in medullated fibers appears pure yellow. 

 The regions which contain mixtures of medullated fibers and 

 other cortical substance, appear various shades between pure 

 gray and pure yellow. Kaes distinguished five color grades in the 



• 3. P- 4-5- 



'i.P- 3- 



Note — The References to Kaes's papers are given by means of the numbers 

 of the papers in the bibliography at the end of this article. The page numbers 

 given refer in every case to the paging of the reprints, and not to the paging of 

 the periodicals in which the papers originally appeared. The attempt is made 

 to refer each important statement used in the summary to the exact page of the 

 article from which it was taken. 



