415 



freezing-point, excretine crystallizes readily and in large quantity in 

 the clear alcoholic extract of faeces; this method I employed as 

 often as possible, to prepare enough excretine for its chemical ana- 

 lysis ; but the cold weather not lasting long enough, and this season 

 having been remarkably mild, I was compelled to adopt a modifica- 

 tion of the process by milk of lime, described in my former commu- 

 nication. 



Having prepared a sufficient quantity of excretine, partly by the 

 action of cold, and partly by means of milk of lime, the chemical 

 composition of this substance was now determined. A qualitative 

 analysis showed it to consist of carbon, hydrogen, sulphur and 

 oxygen*; there was no water of crystallization present. Oxide of 

 copper was employed at first for the combustions, but they were 

 subsequently undertaken with chromate of lead, on account of the 

 large proportion of carbon that excretine contains ; no substance 

 having been found to combine with it, its atomic composition was 

 calculated from the assumption that one equivalent contained one 

 equivalent of sulphur ; and the following formula was obtained : 



78 eq. Carbon 468 



78 eq. Hydrogen 78 



1 eq. Sulphur 16 



2 eq. Oxygen 16 



Atomic weight of Excretine 578 



I shall not add more at present as to the properties of excretine ; 

 the plate which accompanies the paper illustrates the shape and 

 arrangement of its crystals. 



In my former communication I had stated that when the tissue of 

 the spleen is submitted to a process of analysis similar to that adopted 

 for the extraction of excretine, a substance closely allied to choleste- 

 rine is obtained. This subject being one of great importance in a 

 physiological point of view, I have resumed the investigation, and 

 placed beyond doubt that this substance is really cholesterine. Its 



* In my former communication I had erroneously stated that excretine con- 

 tained nitrogen, which resulted from my not having been able to prepare a suffi- 

 ciently large quantity of the substance ; and, moreover, it might not have been 

 perfectly pure. 



