On Protagon 



101 



of a comparison of various samples by a quantitative method. We have 

 therefore endeavoured to determine some physical constants of protagon, 

 namely, the specific rotatory power and the refractive index of its solution. 

 Some difficulty was experienced in finding a solvent which would dissolve 

 a sufficient amount of protagon without the use of higher temperatures. 

 We found that protagon was comparatively soluble in pyridine, even at 

 room temperature. By making our determinations at 30°, a 3 per cent, 

 solution could be used. The polarimeter was a Laurent apparatus. The 

 determinations were made in a 10 cm. tube at 30"" with sodium light. The 

 refractometer was a Pulfrich instrument. A high density prism was em- 

 ployed. The pyridine used was Kahlbaum's pyridine, and had at 30'" the 

 lefractive index lo062. The results are given in the following table : 



The results for the specific rotatory power agree well with each other, 

 especially if it is considered that the actual reading taken was very small. 

 They stand in striking contrast to the observations of Rosenheim and 

 Tebb, which were published shortly after our first preliminary communica- 

 tion on this subject had appeared. According to these authors, the specific 

 rotatory power of protagon varies between 2-7" and 7-5°, and thus demon- 

 strates again the composite nature of protagon. As Rosenheim and Tebb 

 include, under the term protagon, the substance prepared according to 

 Couerbe's method for cerebrote, substances insoluble in acetone and 

 substances soluble in acetone, and as most of these substances differ in 

 their chemical composition both inter se and from protagon, their physical 

 properties could hardlj^ be expected to show any agreement. 



From our observations we conclude that different methods of extraction 

 isolate from brain a substance, protagon, of a definite and constant chemical 

 composition, which will retain this composition after repeated recrj'stallisa- 

 tion and possesses definite and constant physical properties. These facts are 

 quite independent of the question to be discussed later, as to whether this 

 substance, protagon, is a definite chemical compound or not. 



The Action of Warm Alcohol upon Protagon. 



We have already seen that the plain postulate, that investigations on 

 the nature of protagon should be made on protagon and not on some crude 

 product po.ssibly containing protagon, has not alwaj's been fulfilled. These 

 observations need therefore not be taken into consideration. Nor can the 



