CONTENTS OF THE LARGE INTESTINE. 293 



The first accurate analyses of the faeces were made by Berzelius ; but the great ad- 

 vances which have been made in physiological chemistry since that time have enabled 

 later observers to arrive at results much more definite and satisfactory. Marcet has lately 

 discovered a crystallizable substance peculiar to the human faeces ; and we have recently 

 shown that probably the most important excrement! tious principle discharged by the 

 rectum is derived from the bile and is a peculiar modification of cholesterine. Most of 

 our statements concerning the composition of the faeces in health will be derived from 

 the researches of Wehsarg and of Marcet and from our own observations. 



The proportions of water and solid matter in the faeces is variable. Berzelius found, 

 in the healthy human faeces, V3'3 parts of water and 26'7 parts of solid residue. The 

 average of seventeen observations by Wehsarg was precisely the same. In the observa- 

 tions of Wehsarg, the mean quantity of solid matter discharged in the fasces in the twenty- 

 four hours was 463 grains, the extremes being 882'8 grains and 251-6 grains. The pro- 

 portion of undigested matters in the solid residue was very small, averaging but little 

 more than ten per cent., the mean quantity in the twenty-four hours in ten observations 

 being but 52'5 grains. This was found, however, to be exceedingly variable ; the largest 

 quantity being 126*5 grains, and the smallest, 12'5 grains. 



Microscopical examination of the faeces reveals the various vegetable and animal struct- 

 ures which we have referred to as escaping the action of the digestive fluids. Wehsarg 

 also found a "finely divided faecal matter" of indefinite structure, but containing partly 

 disintegrated intestinal epithelium. Crystals of cholesterine were never observed. When- 

 ever the matter is neutral or alkaline, crystals of the ammonio-magnesian phosphate are 

 found. Mucus is also found in variable quantity in the fasces, with desquamated epithe- 

 lium, and a few leucocytes. 



The quantity of inorganic salts in the faeces is not great. In addition to the ammonio- 

 magnesian phosphate, phosphate of magnesia, phosphate of lime, and a small quantity of 

 iron have been found. The chlorides are either absent or are present only in small 

 quantity. 



Marcet has pretty generally found in the human faeces a substance possessing the 

 characters of margaric acid, and volatile fatty acids; the latter free, however, from 

 butyric acid. Cystine is mentioned as an occasional constituent of the faeces. He also 

 found a coloring matter, which is probably a modification of biliverdine. 



In 1854, Marcet described a new substance in the human fasces, which he called excre- 

 tine, and an acid called excretoleic acid, which he supposed to be a compound of excre- 

 tine. These substances and the one which we described in 1862, under the name of ster- 

 corine, are, as far as we know, the only principles that have been recognized as charac- 

 teristic of the normal faeces ; and the stercorine we have found to be one of the most dis- 

 tinct and important of the excrementitious principles in the body. The relations of 

 excretine to the process of disassimilation of the tissues have not been so clearly indicated. 



Excretine and Excretoleic Acid. Excretine was obtained by Marcet from the healthy 

 human fasces in the following way : The fseces were first treated with boiling alcohol 

 until nothing more could be extracted. This alcoholic solution was acid and deposited 

 a sediment on cooling. Milk of lime was then added to the solution, producing a yel- 

 lowish-brown precipitate and leaving the fluid of a clear straw-color. The precipitate 

 was then collected on a filter, dried, afterward agitated with ether and filtered, forming 

 a clear, yellow solution. In from one to three days, beautiful, long, silky crystals of ex- 

 cretine were formed, generally collected into tufts adhering to the sides of the vessel. 

 Examined by the microscope, these were found to consist of acicular, four-sided prisms 

 of variable size. This substance is insoluble in water, slightly soluble in cold alcohol, but 

 is very soluble in ether and in hot alcohol. Its alcoholic solutions are faintly though dis- 

 tinctly alkaline. Its fusing-point is from 203 to 205 Fahr. It may be boiled with 

 potash for hours without undergoing saponification. Apparently, the quantity of excre- 



