MICRO-CHEMICAL EXAMINATION OF EXTRACT OF FLESH. 
201 
To obtain a further clue to the nature of the crystalloids, as they appear 
under the microscope, and in some measure to separate them, advantage may 
be taken of the different solubilities of the salts in alcohol. Portions of 
several of the extracts were digested in strong alcohol for some weeks, the 
alcoholic solutions decanted and evaporated to extract consistence. The re¬ 
markable differences which presented themselves in the various examples we 
shall have occasion to comment upon. 
This, or indeed any process by which the separation of one principle from 
another can be effected, is of great importance, for the resemblance between 
the crystalline forms of some of the constituents proper to well-prepared 
extract is so great as to make it, at times, a matter of extreme difficulty, 
depending even more upon experience and judgment than npon actual che¬ 
mical data, to discriminate with certainty amongst them. We need not wish 
a better instance of ambiguity than that afforded by the two most important 
constituents of extractum carnis, namely, kreatine and phosphate of potash. 
It would be exceedingly difficult to describe the forms assumed by these two 
bodies in their various modifications, in terms which would not apply almost 
equally to either; and though a little practice and observation would enable 
a microscopist to distinguish between them in most cases, one can scarcely 
help feeling the want of some more positive evidence, if it be only to carry 
conviction to others. We have, since the greater portion of this paper was 
written, accidentally alighted upon a fact which may possibly be of value in 
this way. About a year ago, to avoid some trifling difficulties of manipula¬ 
tion, subsequently overcome by other means, we mounted a series of speci¬ 
mens of extract, having previously mixed them with a little pure glycerine, 
and set them aside without much intention of again referring to them. On 
examining them a few days ago, the appearance the slides presented was that 
of an even film of brown extractive with a few large crystals here and there, 
evidently all of them of the same chemical nature. By subsequent experi¬ 
ment we found that kreatine is soluble to a considerable extent in glycerine, 
and we therefore conclude the crystals in question to be those of phosphate 
of potash. Want of time has prevented onr experimenting further in this 
direction, but the subject merits the attention of future observers. 
The reaction of kreatinine with bichloride of platinum suggests a method 
of estimating the amount of kreatine in meat-extract. A portion of the 
extract is dissolved in water, acidulated with hydrochloric acid and heated, 
in order to convert the kreatine into kreatinine, evaporated, and solution of 
bichloride of platinum added. The double chloride of platinum and krea¬ 
tinine should separate in long prisms. These we have never obtained to our 
satisfaction, but the microscopical appearance of the fluid after the addition of 
the platinum salt and concentration is very peculiar, and we are not without 
hope that further investigation in the same direction may lead to practically 
useful results, though as yet we have not had time to complete the inquiry. 
Concerning the colloid constituents there is not much to be said. The 
proportion of uon-crystallizable bodies present may be determined by dialysis, 
and how much this may vary will be gathered from our notes on two of the 
specimens named. Two hundred and fifty grains of our preparation made 
with cold water yielded 18'58 grains of colloid, about per cent, of the 
whole weight: that prepared with hot water contained a larger proportion. 
The Australian extract yielded, from 250 grains, no less than 97 grains, or 
nearly 39 per cent., of colloids. As these represent two extremes in quality, 
and our other experiments correspond with the indication they give, we may 
justly infer that dialysis affords a fair means of nearly ascertaining the proxi¬ 
mate value of commercial extracts. The diffusate of all the samples yielded, 
on evaporation, a light brown residue, which became an almost solid mass of 
crystals. 
