which again dissolves in an excess of the precipi

tant.

of the ashes

of the juice

of flesh,

If we compare with the characters just described Characters those of the ash of the juice of flesh, we observe the following facts. The ashes of the juice of flesh, in the case of the ox, horse, fox, and roe-deer, give with water a strongly alkaline solution, which is precipitated, first white, then yellow, by neutral nitrate of silver; and the mixture, after complete precipitation, is perfectly neutral. This proves that the they conashes contain salts of phosphoric acid, with 2 atoms phosphates (pyrophosphates), and with 3 atoms (tribasic phos- phosphates. phates) of fixed alkaline base.

If these ashes are mixed with nitric acid, dried up, and again ignited, by which means the chlorine of the alkaline chlorides is expelled, and the metals added to the phosphates in the form of oxides, the proportion between the white and the yellow precipitate with nitrate of silver is altered, the quantity of the yellow precipitate being increased; but the two colours of the precipitate are constantly observed.

tain pyro

and tribasic

of the juice

of fowl con

The ashes of the juice of the flesh of fowl give The ashes a different result. The aqueous solution precipitates nitrate of silver pure white; the ashes, therefore, contain alkaline pyrophosphates; and when they are acted on by nitric acid and again ignited, the soluble portion still precipitates nitrate of silver only white, although an additional quantity of alkali is thus added to the phosphate originally present.

H

tain pyrophosphates

From this it follows, that the juice of the flesh of and meta- fowl must contain a certain though small quantity phosphates. of alkaline phosphate with 1 atom of fixed base

Proportion

of alkalies

phoric acid.

(metaphosphate), since, otherwise, after the action of nitric acid on the ashes, a certain quantity of phosphate with 3 atoms of fixed base (tribasic phosphate) must have been produced, and thereby a yellow precipitate must have been formed, to a corresponding extent, in the nitrate of silver.

The whole amount of alkalies, therefore, present to the phos. in the juice of the flesh of the ox, horse, fox, and roe-deer, is not sufficient to convert the phosphoric acid of the juice entirely into the so-called neutral salt, that is the salt with 3 atoms of fixed base. In the fowl, the whole of the alkali is not even sufficient to convert the phosphoric acid entirely into the salt with 2 atoms of fixed base.

The organic

acids in the juice are

I have mentioned in a preceding part of this memoir, that the juice of flesh, even before all the phosphoric acid has been precipitated by baryta, at a period, therefore, when it can contain no baryta dissolved, acquires an alkaline reaction.

From this it is plain, that the organic acids present in the juice, the lactic and inosinic acids, &c., taken together, are not in sufficient quantity to form the alkalies. neutral salts with the alkalies contained in it, potash

not sufficient to neutralise

and kreatinine; and this necessarily implies that the acid reaction of the juice of flesh is caused by the presence of acid salts of the alkalies with the three acids-phosphoric, lactic, and inosinic acids. Inosi

The acidity depends on sence of

of the juice

nic acid constitutes too small a part of the juice to allow us to ascribe to it a perceptible share in producing the acid quality of that fluid; and this acidity depends, therefore, on the presence of acid alkaline lactate and acid alkaline phosphate (phosphate with one atom of alkali); or, in other words, and phosof neutral alkaline lactate and phosphate, along acids. with free lactic and phosphoric acids.

It is obvious, that these two acids are shared between the bases present, and that the amount of free acid present must stand in a definite relation to the quantity of the bases.

Between the two acids, so far as they are uncombined, an equilibrium is established; the quantities of the free acids are proportional to their affinity or power of combination.

If we suppose the quantity of one of these free acids to be by any means increased in the juice of flesh, that portion of the other, which is free, must in like manner increase; and if, by any means, the amount of the one free acid be diminished, the free portion of the other must diminish in the same proportion, so that a new equilibrium may be established between the free portions of both. If, for example, a portion of phosphoric acid be added to that present in the juice, a part of this must seize on a part of the alkali of the alkaline lactate; thus a new quantity of acid phosphate of the alkali will be formed, and a corresponding amount of lactic acid set free. Exactly in the same way must a

the pre

free lactic

phoric

Equili

brium be

tween these

free acids.

When either the organic acids or the

acid are removed,

100 CHANGES OF THE BLOOD DURING DIGESTION.

corresponding quantity of phosphoric acid be set free, when the amount of lactic acid present is in any way increased.

Now, since the quantity of phosphoric acid in the juice is sufficient to neutralise all the alkali present, while the organic acids are present in smaller proportion and do not suffice to form neutral salts with the alkali, it follows that the removal of lactic acid would give rise to the production of neutral phosphates, and the removal of phosphoric acid would cause the formation of neutral lactates, along with free alkali.

The salt of phosphoric acid, which is formed when all organic acids are removed from the juice of flesh, phosphoric although neutral in composition, has an alkaline reaction; and when all the phosphoric acid is the residue removed, there are left salts of organic acids, which, from the presence of free alkali, also possess an alkaline reaction.

the

The preceding considerations naturally lead to the explanation of some processes in the animal organism. If the stomach obtain from the blood the same acids, which we have found to exist in the juice of flesh, the blood must possess, during digestion, a stronger alkaline quality than it has in the normal state; and consequently, if the blood is to preserve its normal condition, it must either obtain from the muscles a supply of acid, exactly equal to that which has passed into the stomach, or the excess of alkali must be conveyed to the muscles, or secreted

by the kidneys. If the urine of the animal were acid before digestion, it must, on the latter supposition, become, during that process, transiently neu tral or alkaline; if it contained a certain quantity of free alkali, that must be increased.

The function of the kidneys, as has long been known, consists in the preservation of an equilibrium in the quality of the contents of the blood; and this includes the removal of products of the change of matter, and of all such substances as affect the normal quality of the blood. In this point of view What purthe solution of the question, "What purposes does served by lactic acid serve in the organism?" is of peculiar acid?" importance. On this point I have made some éxperiments, which may perhaps assist us in approaching nearer to the solution.

pose is

the lactic

does not

I have, in the first place, repeatedly endeavoured Lactic acid to detect the presence of lactic acid in fresh urine, occur in healthy possessing the usual acid reaction. But I have not urine." been fortunate enough, with the aid of the same process by means of which I succeeded in demonstrating its presence in the juice of flesh, to detect even a trace of lactic acid in the urine of healthy young men. The urine was evaporated in the water-bath to the consistence of syrup, mixed with diluted sulphuric acid, and the acids thus set free taken up by alcohol. The alcoholic solution was evaporated in the water-bath to a thin syrup, to which half its bulk of alcohol and then ether were added, until no more turbidity ensued. If lactic