W. Koch and M. L. Koch 429 



If it were desirable to recognize the chemical identity of the much abused 

 protagon, the sulphatides might be considered as purified products. Pro- 

 tagon could be much more safely calculated from the lipoid sulphur than 

 from the lipoid sugar as Noll 12 has attempted. The sulphur content of 

 protagon preparations, when it has not been simply ignored, is variously 

 reported as 0.5 and 1.0 per cent. 



Anatomical distribution. The sulphatides, like the cerebrosides, increase 

 parallel with the growth of the medullary sheath and may be considered 

 as essential constituents of that structure. The fact that the sulphatides, 

 as the result of more recent work, have been found to be pretty generally 

 distributed in other tissues, indicates that they might occur in the cell 

 body of the neurone, although a comparison of the analyses of cortex and 

 corpus callosum does not make this very probable. The sulphatides have 

 an important function in the maturing of the nerve fiber and give the 

 Weigert staining reaction in a very characteristic manner. 



Physiological significance. Their colloidal nature and the peculiar com- 

 bination into which the sulphatides enter with potassium, suggests that 

 they may have an important relation to the nerve impulse and to the phe- 

 nomena of conductivity in general. 



Organic extractives and inorganic constituents. 



Chemistry. This group represents essentially the water-soluble, non- 

 colloidal constituents of the nervous system. The older method of esti- 

 mating the inorganic constituents by the ash has been abandoned as too 

 inaccurate. The principal reason for reporting the above group is to give 

 an idea of the ratio between the colloidal and non-colloidal constituents. 



Anatomical distribution. The group occurs in large quantity in the 

 cell body, although some is also present in the axon of the nerve fiber. 



Physiological significance. This group is a rough index of the amount 

 of metabolic activity going on in the tissue, as it represents at the same 

 time the end products of chemical activity, as well as the culture media 

 from which the more complex combinations are built up. 



Undetermined (cholesterol). 



This fraction is represented in the nervous system to a certain extent 

 by cholesterol, which has not been directly estimated. Besides this, how- 



O 



II 

 (Phosphatides) x O S O (Cerebrosides) y 



II 



O 



containing 2.0 per cent sulphur, 42.9 per cent cerebrosides, and 51.2 per 

 cent phosphatides. Then we have, 



(Lipoid sulphur X 50) = ^ rf su , hat;des ; n dry substance . 

 weight of dry substance 



12 Noll, A. : Zeitschr. f. physiol. Chem., xxvii, p. 370, 1899. 



