CONSTITUENTS OF THE NERVOUS SYSTEM. 575 



remark also applies to the nuclein, which v. JACKSCH l found in large 

 quantities in the gray substance. Neurokeratin, which was first detected 

 by KTHNE, and which partly forms the neuralgia, and as a double sheath 

 envelops the outside of the nerve-medulla under SCHWANN'S sheatn and 

 the inner axis-cylinders, occurs in the nerves, but chiefly, or according 

 to KOCH entirely, in the white substance (KUHNE and CHITTENDEN, 

 BAUMSTARK 2 ) . 



The so-cailed protagon has been considered as one of the chief con- 

 stituents, perhaps the only constituent (BAUMSTARK), of the white 

 substance. This protagon, according to most investigators, is only a 

 mixture of phosphatides with the non-phosphorized cerebron or with 

 a mixture of cerebrosides (see below). There does not seem to be any 

 doubt that these last, especially the cerebron as well as lecithin and cephalin, 

 occur preformed in the brain and nerves. From the investigations 

 made thus far it is difficult to state with positiveness whether the last 

 two mentioned bodies (which have been discussed in Chapter V) belong 

 to the gray or white substance. According to KOCH they occur much 

 more abundantly in the white substance. FALK S prepared a phos- 

 phatide from human brain, which behaves essentially like cephalin 

 and also yields cephalinic acid, which is difficult of characterization. 

 The strikingly high nitrogen content is remarkable, namely in one prepara- 

 tion 2.905 per cent and 2.76 per cent in another. The phosphorus 

 content was 3.28 and 3.16 per cent. The relation P:N is correspond- 

 ingly about 1:2. The isolated substance is a diamido-phosphatide 

 while the cephalin thus far investigated is a monamido-phosphatide. 

 Under these circumstances, irrespective of the purity and the chemical 

 identity of the isolated substance, we are not warranted in calling this 

 substance cephalin, as was done by FALK. On the other hand it is also 

 questionable whether we are warranted in including cephalin among the 

 lecithins as done in the text on page 234. The observations of KOCH 4 

 show that at least the human and ox brain contain jecorin, and that 

 the lipoid sulphur occurs, much more abundantly, in the white than in 

 the gray substance. The same is true for the numerous brain phos- 

 phatides described by THUDICHUM S under different names, and whose 

 chemical individuality has not been sufficiently established; cholesterin 

 chiefly occurs in the white substance. Fatty acids and neutral fats may 



1 Pfliiger's Arch., 13. 



2 Koch, Amer. Joufn. of Physiol., 11; Kiihne and Chittenden, Zeitschr. f. Biologie, 

 26; Baumstark, Zeitschr. f. physiol. Chem., 9. 



3 Bioch. Zeitschr., 16. 



4 Zeitschr. f. physiol. Chem., 53. 



5 Thudichum, Die chemische Konstitution des Gehirns des Menschen und der Tiere, 

 Tubingen, 1901. 



