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XI. An Account of the Organic Chemical Constituents or Immediate Principles of 
the Excrements of Man and Animals in the Healthy State. By W. Marcet, 
M.D., F.C.S., formerly President of the Edinburgh Medical Society , Corre- 
sponding Member of the Socidte de Biologie of Paris, and Member of the Parisian 
Medical Society. Communicated by Francis Marcet, Esq., F.R.S., Geneva. 
Received June 14, 1854, — Read June 15, 1854. 
The following investigations on the immediate principles which constitute the 
evacuations of Man and animals were undertaken with the view of endeavouring — 
1st. To determine some of the modifications which the unabsorbed part of food 
undergoes in the alimentary canal. 
2nd. To obtain an insight into the nature of the secretions yielded by the glands 
and mucous membrane of the colon and rectum. 
3rd. To extend our pathological knowledge; and afford new means of diagnosis, 
by applying a method of analysis to healthy human evacuations, thus affording to 
physicians and pathologists an opportunity of examining these matters in a morbid 
state. 
I had proposed, in the first instance, to confine my researches to healthy human 
evacuations, but having detected a method of analysis which enabled me to obtain 
several of their immediate principles in the pure state, I was induced to continue 
the investigation with reference to the castings of various carnivorous, herbivorous , 
and granivorous animals. The castings of the Tiger, Leopard, Dog, Crocodile, and 
Boa were first examined. Then those of the Dog (fed upon bread), Horse, Sheep, 
Wild Boar, Elephant, and Monkey ; and, lastly, the castings of Fowls. 
1. Of the Healthy Human Evacuations. 
The results obtained from the study of the nature and composition of healthy 
human evacuations, together with the method of investigation employed, have been 
condensed into a synoptic table annexed to the present communication. 
It is superfluous to dwell upon the odour, colour and consistence of human faeces ; 
their reaction is constantly alkaline, and they yield but a very weak extract to di- 
stilled water. This alkaline reaction is common to the castings of every animal, and 
is very probably owing to the presence of ammoniaco-magnesian phosphates, the 
only strongly alkaline immediate principle which I have obtained from excrements, 
and which, being soluble, though sparingly, in hot water, is the cause of their alka- 
line nature. 
2 M 
MDCCCLIV. 
