276 
OR. MARCET ON THE IMMEDIATE PRINCIPLES OF 
extract of faeces had caused the formation of the precipitate which has been described 
as composed of excretine, margaric acid, colouring matter, and lime. The filtrate 
from this precipitate having- been concentrated on the water-bath, a scanty amor- 
phous deposit occurred floating- in the solution, which, when viewed under the 
microscope, showed no crystalline structure. The concentrated fluid allowed to 
stand for several days, yielded no crystals, but merely an amorphous residue. By 
distilling- it with water in a small retort, a few drops of sulphuric acid having 
previously been added, I obtained a colourless acid fluid, having a strong smell, 
resembling that of butyric acid, which I at first considered to be owing to the 
presence of that substance; but on treating this fluid with lime or baryta, I failed 
to obtain any crystallized salt, showing that butyric acid was not present, and 
consequently it cannot be considered as a constituent of human evacuations. The 
alcoholic extract concentrated on the water-bath was also treated with ether ; the 
ethereal solution obtained, decanted and allowed to evaporate spontaneously, yielded 
on several occasions crystals of excretine. 
From the above investigations, I may conclude that human evacuations in the 
healthy condition contain : 
1st. A new organic immediate principle, having a crystalline structure and an 
alkaline reaction, which I propose calling Excretine. 
2nd. A substance possessing the characters of margaric acid, which, though not 
constantly present in human evacuations, is generally found as one of its 
constituents. 
3rd. A colouring matter analogous to that of blood. 
4th. A pure olive-coloured fatty acid, which I propose to call Excretoleic acid. 
5th. Volatile fatty acids, free, however, from butyric acid. 
I shall now endeavour to relate as briefly as possible the circumstances and results 
which attended the examination of the castings of various animals, the method of 
analysis which I employed being similar to that already followed for the investigation 
of human evacuations. 
2. Castings of Carnivorous Animals. 
1st. Castings of the Tiger. — Newly- passed Tiger’s excrements, obtained from the 
Zoological Gardens in small lumps, were of a pale colour, had a peculiar nauseous 
smell, and an alkaline reaction. Having previously been washed with a small 
quantity of water, they were boiled with alcohol, and yielded a pale-coloured alco- 
holic extract. The solution, left undisturbed for twenty-four hours, gave no deposit, 
its reaction was slightly acid ; milk of lime added to the extract produced a nearly 
white precipitate, which, after having been dried upon filtering-paper, was treated 
with ether, both hot and cold, until nothing more could be separated from it. The 
