2*4 MANUAL OF HISTOLOGY. 



acid, having the empyrical formula C 3 H 9 P0 6 . It is a bibasic ether-acid 

 of glycerin. 



(OH 



C 3 HJOH 

 (P0 4 H 2 . 



Glycerophosphoric acid is to be found combined with various matters 

 in the yelk of the ovum, in cerebral substance, and in the bile. 

 (Comp. 20, Lecithin.) 



The neutral fats, however those glycerin ethers already mentioned 

 above are the compounds of most ordinary occurrence and greatest 

 importance in the system. 



From the fact that in our n'-atomic alcohol, 1, 2, or 3 atoms of H of 

 the hydroxyl may be replaced by the acid radical, we have derived three 

 series of fats known as monoglycerides, diglycerides, and triglycerides . 



The neutral fats occurring naturally belong only to the last group 

 the triglycerides of many acids. 



Glycerin finds its way into the body with the neutral fats of the 

 food. It becomes free upon the saponification of these, and must again 

 re-combine with the fatty acids on the formation of fats in the tissues, 

 occurrences in regard to which we are still in the dark. The physio- 

 logical decomposition products of glycerin are also still obscure. 



17. 



The fatty acids of the system belong to two natural series, of which 

 one is arranged after the formula, C n H 2n 2 ; the other C n H 2n _ 2 2 . 



Among the numerous monobasic acids of the first group, some of the 

 lower or fluid fatty acids do not possess the characters of tissue elements, 

 but rather those of decomposition products. 



Formic Acid, CH 2 2 . 



Has been met with by Scherer and Miiller in the fluids with which 

 muscle, the brain, and the spleen are saturated ; also in the thymus gland 

 (Gorup-Besanez), in sweat in considerable quantity (Lehmann), and the 

 blood of dogs after a prolonged sugary diet (Boucliardat and Sandras). 

 It is also found pathologically in blood. Many of these statements ap- 

 pear, however, questionable. 



Acetic Acid, C 2 H 4 O a . 



Is a constituent of the juices of muscle and the spleen (Scherer}. Further, 

 it is to be met with in the thymus gland, and has been observed in the 

 perspiration. Acetic acid is also known as one of the ingredients of the 

 gastric juice ; it occurs probably also in the fluids of the brain. Finally, 

 it appears as an occasional constituent of the blood after brandy pota- 

 tions. 



Butyric Acid, C 4 H 8 O 2 . 



Appears in flesh and the juices of the spleen {Scherer) ; also in the milk, 

 sweat, and secretions of the sebaceous follicles of many parts of the body, 

 as, for instance, on the genitals : in the urine also (?). Its presence in 

 blood seems doubtful (Lehmann). It is found also in the contents of the 



