14 MITSCHERLICH ON CHEMICAL REACTIONS 
large quantity in these parts of the organism ; but they entirely 
disappear in the rectum and in the faecal matter. M. Remack 
first drew my attention to this subject, and subsequently M. 
Purkinje, M. Bohn, and my brother have had frequent oppor- 
tunities of observing them. It is very probable that, besides 
digestion, a true alcoholic fermentation takes place in the intes- 
tinal tube, which occasions flatulencies. 
The blood which surrounds the intestinal tube dissolves the 
carbonic acid which may disengage itself from the lungs without 
recourse to other channels. These organized bodies, ordinarily 
of an elliptic form, have two transparent points; sometimes they 
enclose a granular mass like those of the ferments. 
MM. Boutron and Frémy have recently proved that lactine 
is converted into lactic acid under the influence of caseum, and 
that this combines with the acid formed. Moreover, on sepa- 
rating the caseum from its combination with the lactic acid, by 
means of carbonate of soda, a new quantity is produced. The 
composition of lactic acid is such that it is represented by milk- 
sugar, less a certain quantity of water. I have repeated these 
experiments with the same result; but as, in this reaction, a 
combination of caseum and lactic acid is formed, we must sup- 
pose that the affinity of the lactic acid for the caseum intervenes 
in the phenomenon. Nevertheless the coagulation of milk, in 
the preparation of cheese, appears owing to other causes, since 
runnet is commonly employed to effect it. 
It is commonly supposed that it is the internal part of the 
stomach of the calves which determines the coagulation of the 
milk. It is not so, however: the runnet which I have been able to 
procure was prepared by means of the mucous and the muscular 
membranes taken from the stomach, in throwing back the peri- 
toneum; but I have been very well able to coagulate milk by 
employing other parts of the peritoneum ; for example, with the 
part which covers the cecum. If the precaution be taken to 
raise the temperature of the milk a little, the coagulation is pro- 
duced in a few hours, either by suspending in it the membrane 
itself, or by pouring into the milk a warm infusion of the latter. 
The membrane and its infusion have no acid reaction, and the 
milk remains neutral during its coagulation. 
The chemical combinations which are effected by means of 
substances which only act by contact have much analogy with 
those which are effected when, for example, a body combines 
