The Chemistry of Cookery

accordance with this the extraction of the juices of meat is effected more rapidly by warm than by cold water; but there is a limit to this advantage, as will be easily understood from what has already been explained in Chapter III. concerning the coagulation of albumen, which at the temperature of 134° Fahr. begins to show signs of losing its fluidity; at 160° becomes a semi-opaque jelly; at the boiling point of water is a rather tough solid; and if kept at this temperature, shrinks, and becomes harder and harder, tougher and tougher, till it attains a consistence comparable to that of horn tempered with gutta-percha. I have spoken of beef-tea, or _Extractum carnis_ (Liebig’s ‘Extract of Meat’), as an extreme case of extracting the juices of meat, and must now explain the difference between this and the juices of an ordinary stew. Supposing the juices of the meat to be extracted by maceration in cold water, and the broth thus obtained to be heated in order to alter its raw flavour, a scum will be seen to rise upon the surface; this is carefully removed in the manufacture of Liebig’s ‘Extract,’ or in the preparation of beef-tea for an invalid, but in thus skimming we remove a highly-nutritious constituent—viz. the albumen, which has coagulated during the heating. The pure beef-tea, or _Extractum carnis_, contains only the kreatine, kreatinine, the soluble phosphates, the lactic acid, and other non-coagulable saline constituents, that are rather stimulating than nutritious, and which, properly speaking, are not digested at all—_i.e._ they are not converted into chyme in the stomach, do not pass through the pylorus into the duodenum, &c., but, instead of this, their dilute solution passes, like the water we drink, directly into the blood by endosmosis through the delicate membrane of that marvellous network of microscopic blood-vessels which is spread over the surface of every one of the myriads of little upstanding filaments which, by their aggregation, constitute the villous or velvet coat of the stomach. In some states of prostration, where the blood is insufficiently supplied with these juices, this endosmosis