150 Journal of Comparative Neurology and Psychology. 



6. Neuridin. 



G. Inorganic bodies. Sodum, potassium, ammonium, calcium and iron, pres- 

 ent either as dissociated ions, or in organic combination. The radicles 

 CI, SO^, PO4, and CO3 are also present as disociated ions or with 

 the cations above mentioned. 



H. Lecithins (Monophosphatids containing one nitrogen molecule in the pro- 

 portion N:P^i:l). The various lecithins from eggs, barley, malt, 

 yeast and brain show variations in the amounts of phosphorus and in 

 the methyl content. 



1. Lecithins (Stearylolely, margeryloleyl, palmityloleyl). 



2. Amido-lecithins (amido-myelin). Contains two nitrogen molecules 



N:P=2:i. 



3. Kephalins (P:N=i:l). 



Kephalin 



Oxykephalin 



Peroxykephalin 



Myelin 



Paramyelin 



Sphingomyelin 



Assurin (N:P:=2:2). 



4. Amido — Kephalins (amido-kephalin P:N^i:2). 

 I. Cerebrins. 



1 . Phrenosin 



2. Kerasin (Thudichum) 



3. Amidocerebrinic acid — glycosid (Bethe) 



4. Phrenin 



:;. Cerebrin acid 



Cerebrin acids 



Sphaerocerebrin 



Cerebrin phosphoric acid (Bethe) 

 J. Cholesterin (occurs both free and in the form of an ester). 

 K. Sulphur compounds (Cerebusulphatides and sulphatids of Thudichum). 

 L. Amidofats (Krinosin and Bregenin). 



As a contrast, Thudichuim's classification alone should he con- 

 sulted (Die chemische Konstitution des Gehirn.s des Menscheu und 

 der Tiere, pp. 89-91), and the reader will also find there a minute dis- 

 cussion of these various products, with particular relation to their 

 chemical reactions. 



It is unnecessary to enter here into the details of the newer 

 methods for the isolation of the various brain .substances. The orig- 

 inal papers must be consulted, of which reference is given in the bibli- 

 ography afifi.xed to this review. It suffices to mention Thudichum's 

 complete isolation methods, the acetone method of Koch for the sep- 

 aration of lecithin, kephalin and cerebrin, Levkxe's methods for the 

 isolation of nucleic acid and the uucleo i)roteids, Koch's modification 



