34 



MANUAL OF HISTOLOGY. 



action of the mammary gland. There seern strong grounds for believing, 

 farther, that grape-sugar is the substance from which it is formed in this 

 process. 



F. Non-Nitrogenous Acids. 



23. 



In considering the fats ( 17), we have already been obliged to refer to 

 two homologous series of acids, partly possessing histogenic properties. 

 We now add here another series, having decidedly the nature of decom- 

 position products. 



In the first place may be mentioned two acids of the lactic-acid group, 

 isomeric combinations, but differing in their constitution the first being 

 derived from aldehyd, the second from ethyl compounds. 



Lactic Acid, C 3 H 6 3 , or 



CH 8 



CH.OH' 



C0 2 H. 



This acid, which is easily formed from amylum or sugary fluids by fer- 

 mentation, gr also from inosite, is found in the gastric 

 juice; further, in the contents of the intestinal 

 canal, as a decomposition product of ingested carbo- 

 hydrates, and also in the brain, and various gland- 

 fluids of the body (?). With bases it forms salts 

 under certain circumstances. 



Among these we have lactate of calcium (C :J H 5 3 ). 2 Ca 

 + 5H 2 (fig. 10), which crystallizes in brush-like 

 groups of very fine needles. 



Another salt, lactate of zinc, is of considerable 

 diagnostic worth in the recognition of lactic acid. 

 Its formula is (C 3 H 5 3 ),Zn + 3H 2 0, and it crys- 

 tallizes in four-sided obliquely-truncated prisms, 

 which present a characteristic clubbed appearance 

 while in process of formation. 



In regard to the source of lactic acid in the body, 



in groups of flue needles. ^here can ^ e no doubt that, where it is not a pro- 

 duct of fermentation, it is derived from the decomposition of histogenic 

 substances. 



CH 2 OH 

 Paralactic Acid, C 3 H 6 3 , or \ CH 2 



C0 2 H. 



This acid, so similar to ordinary lactic acid, differs from it in its salts, 

 which vary in their solubility and amount of water of combination. 



Paralactate of calcium, (C a H 5 3 ) 2 Ca + 4H 2 , has the same crystalline 

 form, but is less soluble than the corresponding salt of ordinary lactic 

 acid. 



Paralactate of zinc, (CgH/X^Zn + 2H 2 , is the same as the crystalline 

 form, but easier of solution in water and alcohol than lactate of zinc. 



Paralactic acid is to be found in muscle, on the death of which it 

 becomes free, giving to its juices their acid reaction. It is also present 

 in bile (Strecker). 



Fig. 10. Lactate of lime 



