THE EXCREMENTS OF MAN AND ANIMALS. 
267 
proves most difficult to remove. By redissolving them, however, in ether, and 
allowing the solution to evaporate spontaneously, the substance may be obtained 
comparatively pure, though not always colourless. I have obtained a nearly colour- 
less solution by filtering the fluid through very finely divided animal charcoal. The 
crystals obtained from this second solution were generally very much larger than in 
the previous case, especially when a little alcohol had been added to the ether. These 
crystals, when viewed under the microscope, were seen to consist of acicular four- 
sided prisms ; they were collected upon a filter, dried and preserved. 
This constituent of human evacuations, which I propose to call excretine, was 
detected in every case of healthy human fceces examined ; it can be obtained very 
easily by the above process, even from a small sample of excreted matter, and 
recognized at once by the silky and very light nature of the tufts. 
It is very soluble in ether or hot alcohol, but sparingly so in cold alcohol, and does 
not precipitate or crystallize on cooling ; its solution in ether and in alcohol has a 
decided though weak alkaline reaction; it is insoluble in water, both cold and hot. 
When suspended in boiling water, excretine fuses into a yellow resinous mass 
floating on the fluid. If dissolved in this state in ether, it again crystallizes when 
the solution is sufficiently concentrated. When treated with water containing any 
of the mineral acids, no decomposition ensues, even if the fluid be evaporated nearly 
to dryness ; nothing is obtained but the above resinous mass, which again yields 
crystals of excretine when dissolved in ether ; excretine does not therefore appa- 
rently combine with mineral acids. When heated upon a platina knife, the crystals 
first fuse, evolving a peculiar aromatic smell ; they afterwards burn with a slight 
flame, disappearing very rapidly, and leaving a brown stain, which, on the further 
application of heat, is completely removed, and no inorganic residue is left behind. 
The fusing-point of excretine was constantly found to be between 95° and 96° 
Centigrade. 
If excretine be boiled for several hours in a solution of potash, no saponification 
takes place; the fused crystals float on the fluid, and if dissolved in ether, the sub- 
stance can again be obtained crystallized. 
The elementary quantitative analysis of excretine and the products of its decom- 
position will constitute the subject of a future inquiry. With respect to its qualita- 
tive composition, I have detected sulphur as one of its constituents, by calcining a 
sample of well crystallized and perfectly white excretine with a mixture of carbonate 
of soda and potash previously ascertained to contain no sulphuric acid. The cal- 
cined mass having been dissolved in water acidulated with pure nitric acid, the 
addition of chloride of barium caused a distinct precipitate. I have also ascertained, 
by the method of Will and Varrentrapp, that excretine contains a small quantity of 
nitrogen. 
I have not yet investigated the products of decomposition of excretine, but if 
nitric acid be added to a hot solution of this substance in alcohol, a brisk action 
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