LACTIC ACID IN THE SYSTEM. 75 



some days in a warm place, its gluten induces such a change that the 

 starcft turns into lactic acid, and the paste becomes sour. 



Of lactic acid there are two kinds ; that derived, as hereafter stated, 

 from muscle juice, is the alpha lactic acid, and that from the Alpha and beta 

 fermentation of sugar the beta lactic acid. As it occurs in lactic acid - 

 the gastric juice, associated with or replacing hydrochloric acid, it is of 

 the beta variety. Whatever may have been the source of this portion 

 of it, whether it has been derived by gastric secretion or through the 

 transmutation of amylaceous food by the saliva, its abundant occurrence 

 in the contents of both the small and large intestines, in which it is rec- 

 ognized by the peculiarities of its zinc and magnesia salts, confirm the 

 conclusion that in this case, at least, the beta form arises from the opera- 

 tion of the digestive juices. 



Lactic acid undergoes rapid absorption through the intestine, and is 

 as rapidly disposed of in the system. Thus Lehmann found, after tak- 

 ing half an ounce of dry lactate of soda, that in thirteen minutes his 

 urine had become alkaline. On injecting the same salt into the jugular 

 vein, it appeared in from five to twelve minutes as carbonate of soda in 

 the urine. 



Berzelius first discovered the existence of lactic acid in the juice of the 

 muscles. Liebig showed that, in quantity, there is more p r0( j u ction of 

 present in this source than is sufficient to neutralize the alkali lactic acid by 

 of all the other liquids or juices of the body. Muscle lac- * 

 tic acid is removed away with rapidity by the lymphatics. Berzelius 

 concluded that its quantity increases in proportion to the exercise the 

 muscle has undergone ; and this would lead to the inference that it is 

 one of the chief products of muscular waste ; for it is not to be supposed 

 that its appearance in muscle juice is because those organs attract it 

 from the blood, in which it pre-exists, derived, perhaps, from the trans- 

 formation of amylaceous substances in the intestine, for the muscles of the 

 carnivora yield as much of it as those of the herbivora ; and though it can 

 not be artificially made directly from albuminous material, yet it would 

 seem that, with urea and ammonia, it might arise from the breaking up 

 of creatine. From glycerine lactic acid may be also developed. When- 

 ever an excess of it is produced in the system, either by muscular action, 

 unusual diet, or imperfect oxidation in the blood, it may be detected in 

 the urine. Under ordinary circumstances, doubtless, very large quanti- 

 ties of it are destroyed in the circulation, giving rise to the production of 

 carbonic acid and water with a disengagement of heat. 



We can not here fail to remark how the process of comminuting the 

 food is carried forward to such an extent that the absorbent These digest- 

 vessels are able to take it up. The action first begins, as has 

 been shown in detail, by cutting and crushing implements, ions. 



