Bauhaus-Universität Weimar

THE DIGESTIVE PRINCIPLE. 
393 
tity of the digestive fluid which is adequate to the solution of a certain 
quantity of albumen, loses its solvent power when diluted. Lastly, 
if it were the part of the acids to enter into combination with the 
products of digestion during their formation, the proportion of the 
acids in the fluid ought to become less as the digestion advances; but 
their proportion undergoes no change. Dr. Schwann infers, there¬ 
fore, that the dilute acids, without themselves undergoing any change, 
aid by their presence in effecting the decomposition of the organic 
substances, just as they aid in the conversion of starch into sugar 
when boiled with it.* 
The artificial digestion by means of the acid infusion of gastric 
mucous membrane may be compared with fermentation, and with 
the cases of decomposition by contact; inasmuch as both in it, and 
in these processes, a very small quantity of the decomposing agent is 
sufficient to produce the effect.! But it results also, from Schwann’s 
observations, that the action of the digestive fluid induces the loss of 
a part of its power, and not the production of a new active principle, 
as in the process of fermentation. Moreover, no carbonic acid is 
developed during artificial digestion, and not the smallest quantity 
of oxygen is necessary to the process, as has been demonstrated anew 
by Schwann in still more accurate experiments. Many substances 
which disturb the progress of the vinous fermentation, likewise in¬ 
terfere with digestion; thus, as Schwann shows, alcoholf and the 
boiling temperature render the digestive principle inert; the same is 
the action, in a less degree, of the neutral salts, and particularly of 
the sulphites. But arseniate of potash, which puts a stop to the 
vinous fermentation, was found by Schwann not to disturb the 
artificial digestive process. 
Chemical properties of the digestive principle.—It must be almost 
impossible to obtain the solvent principle of the digestive fluid in a 
separate state, on account of its active property being so easily de¬ 
stroyed by re-agents. Several of SchwamTs experiments show the 
action of different substances upon it. It is not precipitated when 
the acid of the mixture is neutralised; on the contrary, it is soluble 
in water alone; it is precipitated from the neutral solution by acetate 
of lead, and can be obtained again in an active state from the pre¬ 
cipitate by means of hydro-sulphuric acid. Ferro-cyanuret of po- 
* Although acids are such feeble solvents of organic substances, and particu¬ 
larly of albumen at ordinary temperatures, and even at that of natural digestion; 
yet white of egg when boiled in dilute acids, is, according to Wasmann, (De di- 
gestione nonnulla. Berol. 1839, and Froriep’s Notizen. April, 1839,) very rapidly 
dissolved. He supposes, therefore, that the acids are the essential solvent agents 
in digestion, and that the pepsin has merely the office of rendering their action 
rapid at a temperature at which it would otherwise be slow. 
f 4-8 grains of digestive fluid, or 0-11 grains of dry residue of the fluid, were 
sufficient when diluted for the solution of 60 grains of moist albumen, or about 10 
grains of solid matter. 
X The precipitate thrown down by alcohol in the watery solution of pepsin, when 
re-dissolved in dilute acid, has, however, according to Wasmann, still the power of 
dissolving white of egg, and the other properties of pepsin; and Purkinje states that 
aleohol does not destroy the digestive principle.
        

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