60 Royal Society. 



in human evacuations, he supposes that what is contained in the fat 

 of mutton or beef taken as food must be converted into margaric 

 acid in its passage through the alimentary canal. 



The lime precipitate, freed from excretine and dissolved in alcohol 

 by means of hydrochloric acid, forms a dark port- wine-coloured solu- . 

 tion, from which the margaric acid is deposited. On then adding 

 water to the solution and concentrating it on the water-bath, a flaky 

 colouring matter separates, which, being purified by solution in aether 

 and washing with water, is obtained as a dark-brown or black amor- 

 phous substance, similar to the colouring matter of blood, and to 

 that which Dr. Harley has lately extracted from urine. 



The matters brought down with the lime having been thus ex- 

 tracted, the sediment which spontaneously subsides from the alco- 

 holic solution of faeces before its treatment with the milk of lime, is 

 next examined. This deposit appears to be complex in its nature ; it 

 has a strongly acid reaction, and presents under the microscope small 

 oily globules, mixed sometimes with crystals of excretine and accom- 

 panied by a yellow amorphous matter. By boiling with alcohol and 

 filtration, a residue remains which the author has not yet examined, 

 and two substances are obtained from the filtrate. The first is de- 

 posited on cooling ; when collected and dried on filtering-paper it 

 has a granular character and is quite colourless ; it is very sparingly 

 soluble in aether, fuses by heat, and burns with a bright fuliginous 

 flame, leaving a white residue consisting of phosphate of potash. 

 The author has not yet been able satisfactorily to decide whether 

 this is a pure immediate principle or not; he is inclined to consider 

 it as a combination of phosphate of potash and a pure organic sub- 

 stance. The filtered fluid, after separation of this matter, still con- 

 tains a substance which he has called Excretolic acid. It is obtained 

 by evaporating to dryness, extracting the residue with aether, adding 

 to the sethereal solution alcohol and lime-water, and heating. The 

 acid is precipitated in combination with lime, from which it is sepa- 

 rated by means of sulphuric or hydrochloric acid and solution in 

 aether. The aethereal solution, after being well washed with water 

 to remove mineral acid, yields the pure excretolic acid on evapora- 

 tion. This body is of an olive colour ; it fuses between 25° and 

 26° C, and at a higher temperature burns without residue. It is 

 insoluble in water and in a boiling solution of potash ; very soluble 

 in aether, sparingly soluble in cold alcohol, readily so in hot ; its 

 solutions having a marked acid reaction. The author is disposed to 

 believe that in excrement it is combined in form of a salt, with ex- 

 cretine or a basic substance closely allied to it, which is obtained in 

 the filtrate from which the excretolic acid is precipitated in com- 

 bination with lime in the process of its purification. 



The author failed to obtain evidence of the presence either of 

 butyric or of lactic acid in the clear alcoholic solution of faeces filtered 

 from the precipitate formed by the milk of lime. From the above 

 investigation, therefore, it appeals that healthy human excrements 

 contain : — 



1. A new organic substance, possessing an alkaline reaction, which 

 the author names Excretine. 



