188 DIGESTION. 



the unabsorbed mineral ingredients of the food, and partly from the 

 saline matters of the intestinal secretions. 



Beside the above, the feces contain two crystallizable matters of 

 organic origin, which, though not present in large quantity, are of 

 importance from their chemical characters and the mode of their pro- 

 duction ; namely, excretine and stercorine. 



Excretine. This was discovered and described by Dr. W. Marcet, 1 

 as an ingredient of human feces, though it does not occur in those of 

 the lower animals, either carnivorous or herbivorous. It is a neutral or 

 faintly alkaline crystallizable substance, insoluble in water, but soluble 

 in ether and hot alcohol. It crystallizes in radiated groups of four- 

 sided prismatic needles. It fuses at 96 (204 F.) ? and burns at a higher 

 temperature. It is non-nitrogenous, and consists of carbon, hydrogen, 

 oxygen, and sulphur, in the following proportions: 



It is thought to be present mostly in a free state, but partly in union 

 with certain organic acids, as a saline compound. 



Stercorine. This substance was discovered by Prof. A. Flint, Jr., 

 both in human feces and in those of the dog, and was obtained by him 

 in proportions varying from O.Ot to 0.3 per cent, of the entire fecal 

 mass. It is most abundant in the feces of the human subject, where its 

 average quantity is estimated by its discoverer as about 0.65 gramme 

 per day. It is insoluble in water, soluble in ether and in boiling alco- 

 hol, neutral in reaction, and, like excretine, crystallizes in the form of 

 radiating needles. It differs from excretine, however, in having a much 

 lower fusion point, becoming liquefied at 36 (96. 8 F.). It is regarded 

 as produced by transformation in the intestine from the cholesterine of 

 the bile. 2 



1 Philosophical Transactions. London, 1857, p. 410. 



2 American Journal of the Medical Sciences. Philadelphia, October, 1862. 



