A BRIEF SUMMARY OF THE RESEARCHES OF 

 THEODORE KAES ON THE MEDULLATION OF 

 THE INTRA-CORTICAL FIBERS OF MAN AT DIF- 

 FERENT AGES. 



By Helen Bradford Thompson. 



(From the Neurological Laboratory of the University of Chicago) 



The detailed knowledge which we now possess of the de- 

 velopment of the intra-cortical fiber systems of the human 

 brain from birth to adult years, is largely due to the extended 

 and painstaking researches of Theodore Kaes. The results of 

 Kaes's investigations have appeared in a series of papers in 

 German periodicals, extending from 1891 down to 1900.* Since 

 this extremely valuable material is not, in its present form, easy 

 of access to English students, it seemed worth while to present 

 in these pages, a concise summary of Kaes's results so far as 

 they have appeared. 



The task which Kaes set himself, was that of determining 

 the number and the distribution of the medullated fibers of the 

 various regions of the cerebral cortex at successive ages, from 

 birth to adult years. He assumes the truth of the proposition 

 that the appearance of the medullary sheath means the begin- 

 ning of functional activity in the neurone to which it belongs. 

 If this be granted, it becomes possible to determine by means 

 of the medullation the period at which each of the various 

 groups of intra-cortical fibers becomes functional, and the length 

 of time that functional development continues within each fiber 

 system. The importance of ascertaining these facts is three- 

 fold: i) it furnishes a basis for correlating intellectual growth 

 with the growth ©f the brain ; 2) it serves as a standard for 



See Bibliography. 



