FATS. 81 



of silver to a solution of vaccinate of baryta^ a wliite caseous 

 precipitate is formed, which is soon reduced, and smells strongly 

 of butyric acid. 



Vaccinic acid has, therefore, evidently the same capacity of 

 saturation as caproic and butpic acids together, but probably 

 contains less oxygen. 



In all probability these acids form compounds with glycerin, 

 and exist in butter as distinct fats. 



The brain contains several distinct fats which have been 

 examined by different chemists (Kiihn, Couerbe, Fremy,) and 

 found to contain phosphorus and sulphur. Couerbe has given 

 to these the names of eleencephol, cerebrot, cephalot, and 

 stearaconot. Cephalot is the only one that is saponifiable, 

 and which, therefore, comes under the category of the true fats. 

 Its fatty acid is unknown ; in fact the Avhole subject of the 

 brain-fats requires an entire revision. 



Fremy' has described two fatty acids that exist in the brain 

 in combination with soda, to which he has applied the names 

 of cerebric and oJeophosphnric acids. 



Of the bodies just described, those which act the part of 

 bases, never occur naturally in an isolated state ; and those 

 which act as acids, very seldom. Butyric acid occasionally 

 exists in a free state in the urine, and, according to Gmelin, 

 in the gastric juice, and occasionally in the cutaneous trans- 

 piration. Lecanu states that the margaric and oleic acids 

 exist in a free state in the blood. Some of the fatty acids, as 

 already observed, exist in the bile and in the cerebral matter, 

 in combination with soda, but they are most commonly found 

 united with glycerin. 



The contents of the cells of ordinary adipose tissue are a 

 mixtm'e of stearin, margarin, and olein; and the marrow of 

 the bones has a very similar composition. The relative propor- 

 tions of these three substances varies in the fat of different 

 animals, which is the reason of the different consistence of 

 various fats. The more olein present, the softer and more 

 liquid will the fat be : and those fats in which the olein forms 

 the principal ingredient are called oils. Those of a mean con- 

 sistence are most properly termed fats, while the harder ones 



' Annales de Chimie, 1841. 



