102 THE LACTIC ACID GROUP. 



muscular fibre is discharging its function, (i. e. during the con- 

 traction of muscle,) the only objection to the view that this acid 

 proceeds from the decomposition of the muscular substance itself, 

 is, that hitherto lactic acid has not been produced either by 

 fermentation or otherwise, from any nitrogenous animal matter, 

 either albuminous or gelatinous. We should, however, not make 

 much progress in our physiological enquiries, if we set down 

 as impossible all the processes which we happen not yet to 

 have recognised external to the living body. Recent investigations 

 respecting the various modes of decomposition and the products 

 of albuminous bodies, show that a partial conversion of albuminous 

 matter into lactic acid is by no means an absurd impossibility; 

 for Guckelberger*, who found aldehyde among the products of 

 oxidation of albuminous bodies, points out that in these substances 

 there must be hidden a group of atoms, from which sugar of milk 

 or lactic acid might be produced. He further proved, experi- 

 mentally, that sugar of milk with chromic acid also yields aldehyde ; 

 and, on the other hand, Engelhard t found aldehyde of acetic acid 

 among the products of distillation of lactate of copper. We have 

 already directed attention to the analogy existing between lactic 

 acid, and that frequent product of the metamorphosis of animal 

 matter, metacetonic acid. Hence it would be not at all surprising, 

 if lactic acid were in some manner obtained from the gelatinous or 

 protein compounds. 



Moreover, this view is supported by the consideration that, 

 besides lactic acid, creatine, which is found in the muscular fluid, 

 is often a product of decomposition of muscular substance, since 

 otherwise it would be found in other places besides the urine. 

 Moreover, according to Liebig^s discovery, creatine is decomposed 

 by alkalies into urea and sarcosine, a substance isomeric with 

 lactamide ; hence there would be nothing incongruous in assuming 

 that in the natural metamorphosis of creatine in the animal body, 

 where no sarcosine is found, the creatine is still decomposed into 

 urea, but that, in place of sarcosine, there is an abstraction of water, 

 and that lactic acid and ammonia are formed, in which case, 

 however, we should have to explain what becomes of the ammonia. 

 Moreover, it cannot be supposed that lactic acid passes into the 

 muscular substance from the blood, where it is so easily and 

 rapidly consumed ; yet such must be the case if it comes from the 

 acid formed in the intestinal canal from amylaceous food. 



* Ann. d. Ch. u. Pharm. Bd. (J4, S. 99. 



