408 DE. MAECET ON THE IMMEDIATE PEENCIPLES OE HXMAN EXCREMENTS. 
acid in faeces after a vegetable diet, a fact pre-viously ascertained by LEmm* from micro- 
scopical examination. It -was now important to determine, by actual experiment, 
whether a purely vegetable diet would, according to my former method of investigation, 
determine the presence of an excess of margaric acid in the precipitate obtained by mix- 
ing the alcoholic extract of fseces with milk of lime. I consequently submitted myself 
to a vegetable diet, consisting of bread, potatoes, w^ater- cresses, salad, other green vege- 
tables, wine, beer and tea ; vegetable soup was prepared for me without meat, gravy, or 
butter ; I avoided milk, eggs, &c. Having confined myself exclusively to this vegetable 
diet for four days, I examined the second evacuation passed since the beginning of the 
experiment ; the lime precipitate in the clear alcohol extract was collected on a filter, 
and dissolved in hydrochloric acid ; not only did the substance insoluble in hydrochloric 
acid yield margaric acid, but it contained at least two or three times as much of this 
substance as I had ever obtained by the method in question. I was prevented from con- 
tinuing the investigation from its injurious efiects upon my health, but this experiment 
sufficed to show the influence of a vegetable diet upon excrements. 
I now beg to give an account of some further investigations into the nature and com- 
position of the substance which I proposed to call Excretine. 
This constituent of human fseces I first obtained by adding m ilk of Kme to the alco- 
holic extract of fseces, collecting on a filter the precipitate thus obtained, and subse- 
quently treating it with ether, when the solution yielded by spontaneous evaporation 
very impm’e crystals of excretine, which were purified by repeated crystallizations. This 
method unfortunately yielded so small a quantity of the substance in question that I 
failed to collect enough to determine its chemical composition ; it was therefore found 
necessary to postpone this investigation. Until the month of December 1855, my 
endeavours to extract excretine by a more satisfactory process had failed, when on 
coming to my laboratory one morning after a very cold night, on which occasion the 
temperature of the atmosphere had fallen several degrees under the freezing-point, I 
observed that an alcoholic extract of fseces prepared the day before, and left in an open 
beaker, had lost its fluid nature and assumed a thick or gelatinous consistence ; a sample 
of the mass submitted to the microscope was discovered to be full of slender silky 
crystals, which proved by further examination to consist of excretine ; the thick nature 
of the fluid was owing entirely to the presence of these crystals. It became therefore 
evident that the easiest way of extracting the Immediate Principle in question was by 
reducing the temperature of the alcoholic extract of freces ; and I took advantage of the 
cold nights of last winter to prepare a quantity of this interesting substance *. 
The first crop of crystals being collected on a filter, the alcoholic filtrate )fielded a 
second quantity on the same day or next morning ; in very cold weather sometimes even 
* Having failed to obtain excretine by means of artificial cold, I could not prepare enough of it last 
winter to complete its analysis ; the cold weather of this season has lasted such a short time that it was 
necessary to adopt a modification of the first method ; and thus I was compelled to delay communicating 
my results, for which circumstance I beg to offer my sincere apologies. 
