410 DE. MAECET ON THE BBIEDIATE PEINaPLES OP HOIAN EXCREMENTS. 
subsequently filtered, if necessary, through animal charcoal. This method is attended 
with no difficulty, and enabled me to obtain at once from nine evacuations, as much as 
0'815, or not quite one gramme of excretine ; its only objection is the expense resulting 
from the unavoidable use of large quantities of alcohol and ether. It is very trouble- 
some, and I may say next to impossible, to wash the lime precipitate to such an extent 
as to remove from it every trace of excretine, and consequently the above number must 
be far short of the real proportion of the substance contained in nine evacuations ; I am 
at present engaged with investigations respecting this subject. 
Among the properties of excretine there is one on which I shall add a few words, 
as it appears to me possessed of especial interest. This immediate principle of human 
faeces is not subject to spontaneous decomposition, even when freely exposed to the atmo- 
sphere, and its presence can be detected in excrements long after they have been voided, 
a property which might be serviceable in a medico-legal point of "view. Moreover, 
although I have not yet been able to find out a test for the pm'pose of shovdng the pre- 
sence of excretine in complex mixtures, still the method for obtaining it, which consists 
in the addition of milk of lime to the alcoholic extracts of faeces, will suffice to show 
the presence of very minute quantities of this organic substance even in mixtiues of 
the most complex description. Thus I had no difficulty in obtaining a sample of pure 
excretine from the contents of my laboratory water-closet, consisting of faeces, urine, 
paper, dust and other filth. Between two or three gallons of the above nearly fluid 
mixture were qvaporated to dryness in a water-bath, and the dry residue was exhausted 
with boiling alcohol in the usual way. A small quantity of excretine was deposited m 
the alcoholic extract on cooling ; but on adding lime-water to the solution, collecting 
upon a filter the precipitate thus induced, drying it and washing it with ether, a com- 
paratively large amount of excretine was obtained. 
Having prepared a sufficient quantity of colourless and piue excretine, partly by the 
action of cold upon the alcoholic extract of faeces, and partly by the other method, this 
immediate principle was submitted to chemical analysis. The qualitative examination 
confirmed the existence of sulphur in excretine, and consequently in the combustions it 
was necessary to interpose a tube full of peroxide of lead between the chloride-of-calcium 
tube and the potash apparatus. The presence of nitrogen in excretine was very cai’efully 
looked for by burning the substance mth potassium and testing the fumes evolved 
when a sample of the crystals was heated with lime in a test-tube. I repeated these 
experiments several times with Dr. Dupee, but failed to obtain indications of the 
slightest traces of nitrogen ; it is therefore obvious that excretine contains no nitrogen*. 
The absence of water of crystallization was determined by fusing in the water-bath a 
weighed quantity of the crystallized substance, and then weighing it again, when it was 
not found to have lost any weight ; the experiment was repeated twice with the same 
* In my first communication I stated that nitrogen was present in excretine ; this error resulted from 
having hut a small quantity of substance to operate upon, which, moreover, might possibly not have been 
perfectly pure. 
