GROWTH OF THE CORPUS CALLOSUM 



41 



It is important to consider the factors reponsible for producing 

 the differences between the rapid and the slow growth of the 

 €allosal area during these two periods. We should have infor- 

 mation touching the changes in, 1) histological structure; 2) the 

 degree of myelination; 3) the chemical composition; 4) the 

 change in the percentage of water and anj'^ other modifications 

 occurring during growth, which can be applied. 



1. The callosum is pure white matter, except for a small 

 amount of glia cells, the longitudinal striae and blood-capillaries, 



D mm 



<' 



I 



BODY WEIGHT GRAMS 



50 



too 



150 



200 



250 



Chart lA The continuous line represents the area of the corpus callosum 

 according to body weight, calculated by formula 1; the broken line shows the 

 means of the observed callosal areas. Albino rat. 



and the callosal fibers are without a neurilemma. Koch ('17) 

 found in the dog and in man a great smiilarity of chemical 

 composition represented by the weight of the ether-alcohol 

 extract from the callosum and the intradural nerve roots. From 

 these results Donaldson ('17) concluded that the degree of 

 myelination was probably similar in these two parts of the 

 iiervous system. We know also from Sugita's work that during 

 cortical growth, both the axon and its myelin sheath lengthen 

 and enlarge without disturbing their relative volume relations, 

 and that the very considerable increase in the area of the cortex. 



