EXCREMENTS OF MAN AND ANIMALS. 
647 
mixed with milk of lime. The subsiding lime is of a yellow 
brown colour ; it is dried on filtering paper, and treated with 
ether, cold or hot ; and the solution thus obtained, yields, on 
spontaneous evaporation, beautiful silky crystals, which are 
purified by solution in a mixture of alcohol and ether, re- 
peated filtration through animal charcoal, and re-cry stalliza- 
tion ; they then appear in circular groups, have the form of 
acicular four-sided prisms, and polarize light very readily. 
This crystalline body the author proposes to call Excretine. 
It is very soluble in ether, cold or hot, but sparingly soluble in 
cold alcohol ; its solution has a decided though weak alkaline 
re-action. It is insoluble in hot or cold water, and is not 
decomposed by dilute mineral acids. It fuses between 95° 
and 96° C., and at a higher temperature bums away without 
inorganic residue. When boiled with solution of potash, it 
does not dissolve. As to its qualitative constitution, it is 
found to contain nitrogen and sulphur, though in small pro- 
portions ; the products of its decomposition have not yet 
been investigated. 
“ The author has, in several cases, observed the excretine 
to crystallize directly in the alcoholic solution of faeces before 
the addition of lime, and has scarcely any doubt that it exists, 
for the most part, in a free state in the excrements, and con- 
stitutes one of their immediate principles. As to its source, 
he observes that it appeared in excess w 7 hen a considerable 
quantity of beef had been taken, and in less than the usual 
quantity in a case of diarrhoea attended with loss of appetite ; 
but none could be directly obtained from beef on subjecting 
it to the same process of extraction as faeces. Neither could 
it be found in ox-bile, the urine, or the substance of the 
spleen. From the difficulty of obtaining the contents of the 
human small intestine in a healthy state, its presence or 
absence in that part of the alimentary canal has not yet been 
satisfactorily determined. The lime-precipitate, after having 
been thus thoroughly deprived of the excretine by ether, is next 
treated with hydrochloric acid, and water or alcohol, by which 
means margaric acid is extracted from it. The author is un- 
certain whether the margaric acid of the faeces is free or com- 
bined with excretine ; but he is disposed to conclude that the 
neutral fats are decomposed in the intestinal canal, and their 
acid set free. Not having been able to detect stearic acid in 
human evacuations, he supposes that what is contained in 
the fat of mutton or beef taken as food must be converted 
into margaric acid in its passage through the alimentary 
canal. The lime precipitate, freed from excretine, and dis- 
solved in alcohol by means of hydrochloric acid, forms a dark, 
