94 THE LACTIC ACID GROUP. 



Various authors have assumed that alkaline lactates are present 

 in normal saliva, and have referred the acid reaction which is 

 occasionally noticed in that fluid to the presence of free lactic acid, 

 but in the small amount of solid residue which is left by the 

 saliva, I have never been able to establish with certainty the 

 presence of lactates, even when operating on considerable quan- 

 tities (obtained both from man and from the horse) ; I had, how- 

 ever, an opportunity of collecting large quantities of the saliva 

 of a patient labouring under Diabetes mellitus, and in this case 

 I convinced myself beyond all doubt of the presence of free lactic 

 acid. 



In all the cases of Diabetes mellitus which I have observed, the 

 saliva has had an acid reaction : associated with this symptom and 

 with intense thirst, we sometimes find a copious secretion of saliva, 

 which we have thus a good opportunity of analysing. As the 

 saliva of such patients sometimes (but not always) contains sugar, 

 I took care that it should flow directly from the mouth into alcohol, 

 so as to avoid any possible formation of lactic acid from the sugar. 

 The zinc-salt which was obtained, showed very distinctly the crys- 

 talline form of the lactate. 



Notwithstanding the assumed neutralising property of the bile, 

 the contents of the small intestines of herbivorous, carnivorous, 

 and omnivorous animals, always exhibit an acid reaction, which, 

 however, diminishes towards the ileum ; the acid reaction is strong- 

 est in the duodenum, especially in herbivorous animals. That the 

 acid reaction here depends on the presence of lactic acid, may be 

 most readily shown in the horse, in whose duodenum we find 

 lactate of lime and free lactic acid, especially after the ingestion of 

 amylaceous food. 



Whether the acid reaction of the mucous secretion of fasting 

 animals depends on lactic acid, cannot with certainty be decided, 

 in consequence of the small quantities in which it can be collected. 



I have repeatedly allowed the contents of the duodenum of a 

 recently killed horse (healthy, and killed either in consequence of 

 an accident or from its being affected with malleus) to flow directly 

 into alcohol, and after filtering the fluid while hot, and concentrating 

 it, I have obtained a white granular sediment, which, under the 

 microscope, exhibited the well-known double-brush form of lactate 

 of lime: a quantity collected for analysis contained 2S-97& of water, 

 and in the anhydrous state, 25'831 of lime, 32'982 of carbon, 

 and 4'513# of hydrogen ; this salt was therefore b lactate of limCa 

 The lactic acid was separated in the ordinary mariner from the 



