Reprinted from THE JOURNAL op BIOLOGICAL CHEMISTRY, Vol. XV, No. 3, 1913 



CONTRIBUTIONS TO THE CHEMICAL DIFFERENTIATION 

 OF THE CENTRAL NERVOUS SYSTEM. 



III. THE CHEMICAL DIFFERENTIATION OF THE BRAIN OF THE 

 ALBINO RAT DURING GROWTH. 



BY W. KOCH AND M. L. KOCH. 



(From the Hull Laboratory of Biochemistry and Pharmacology, University 



of Chicago, and the Wistar Institute of Anatomy, 



Philadelphia.) 



(Received for publication, July 1, 1913.) 



The transformations which occur in the brain during growth 

 offer a particularly enticing field for the study of chemical differ- 

 entiation, not alone because of the very great interest attaching 

 to the solution of the problem of the chemical basis of its func- 

 tions, but because its structural differentiation during growth is 

 very marked. On the one hand there is the formation of a large 

 amount of new material composing the medullary sheath of the 

 nerve fibers, and, on the other hand, the appearance of a quantity 

 of a peculiar supporting tissue, the neuroglia. The chemical 

 changes during growth should, therefore, be very marked; and 

 it is of interest to discover how far our chemical methods enable 

 us to follow such obvious structural modifications. 



1 Waldemar Koch died at Chicago February 1, 1912. As Associate in Bio- 

 logical Chemistry at the Wistar Institute of Anatomy and Biology, he spent 

 the autumn of 1910 and of 1911 in Philadelphia working mainly on matters 

 connected with this research. This paper has been prepared in considerable 

 part from results of analyses made by me under the direction of my brother, 

 and from a manuscript written by him. Many additional analyses, which he 

 had planned, have been made and incorporated into the series. The inter- 

 pretations of the results have been left to a large extent, in his words. I 

 have been assisted in its preparation for publication by Professor A. P. 

 Mathews and Dr. H. H. Donaldson, the aid of both of whom I gratefully 

 acknowledge. M. L. KOCH. 



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