3S3 Analysis of the Cerebral Matter of Man, [May^ 



in that case the phosphorus may be considered as amounting to 

 about -j-^th part of the whole. 



Though the substance whose properties have been described in 

 this section has more analogy with tallow and fat than with any 

 other class of bodies, yet it ought not to be confounded with 

 ' ordinary fat. It differs from it pi hicipally by its solubility in 

 alcohol, its capacity of crystallizing, its viscidity, its inferior 

 fusibility, and the black colour which it assumes in melting. 

 Thus, though we class it among fatty bodies, we ought to con- 

 sider it as a particular and new species. 



Sect. V. 



Of the fatty matter of the brain which remains in solution in 

 the alcohol after its cooling. 



We have observed before, that after the alcohol digested with 

 the brain had deposited its fatty matter, it remained of a green 

 colour; and that the third, the fourth, and even the fifth portion 

 of alcohol, which had been digested on the same portion of 

 brain, had a sapphire blue colour. In order to discover the 

 colouring matter we distilled this alcohol. The following are 

 the observations that we made : — 



The green and blue colour is not destroyed by the evaporation 

 of the alcohol, as long as any of the alcohol remains; but as 

 soon as the whole is driven off, the matter acquires a yellow 

 colour, of more or less intensity. Neither the alkalies nor acids 

 change these colours. 



When these operations are performed on the first and second 

 portions of alcohol which have been digested on the same quan- 

 tity of brain, we see, as has been mentioned above, an oily 

 fluid of a yellovv colour precipitate itself to the bottom of the 

 aqueous fluid derived from the humidity of the brain. But this 

 effect does not take place with the last portions of alcohol, be- 

 cause they contain no more water. 



The liquid, at the bottom of which this fatty matter collects, 

 has likewise a yellow colour, a tas^e of the juice of meat, and 

 slightly sweetish, and it gives marks of acidity. While this 

 liquor is hot, the matter remains quite distinct, and seems to 

 have some consistence : but by cooling, or on the addition of a 

 little water, it absorbs humidity, becomes opake, and so mixed 

 with the water that it cannot be separated. We must therefore 

 take advantage of the favourable moment to make this separation 

 in the proper manner. 



From these remarks it is obvious that hot water must be 

 employed to wash tliis substance, and to free it from the soluble 

 matters with which it is mixed. 



