There are two other constituents of lean meat which are very different from either of these, viz. _Kreatine_ and _Kreatinine_, otherwise spelled ‘creatine’ and ‘creatinine.’ They exist in the juice of the flesh, and are freely soluble in cold or hot water, from which solution they may be crystallised by evaporating the solvent, just as we may crystallise common salt, alum, &c. They thus have a resemblance to mineral substances, and still more so to some of the active constituents of plants, such as the alkaloids _theine_ and _caffeine_, upon which depend the stimulating or ‘refreshing’ properties of tea and coffee. Like these, they are highly nitrogenous, and many theories have been based upon this, both as regards their exceptionally nutritious properties and their functions in the living muscle. One of these theories is that they are the dead matter of muscle, the first and second products of the combustion which accompanies muscular work, urea being the final product. According to this their relation to the muscle is exactly the opposite of that of the albuminous juice, this being probably the material from which the muscle is built up or renewed. The following is their composition, according to Liebig’s analyses, and does not support this hypothesis: +----------+----------+------------+ | -- | Kreatine | Kreatinine | +----------+----------+------------+ | Carbon | 36·64 | 42·48 | | Hydrogen | 6·87 | 6·19 | | Nitrogen | 32·06 | 37·17 | | Oxygen | 24·43 | 14·16 | | +----------+------------+ | | 100·00 | 100·00 | +----------+----------+------------+ They appear to undergo no change in cooking unless excessively heated; may be used uncooked, as in cold-drawn extract of meat. The juices of lean flesh also contain a little lactic acid—the acid of milk—but this does not appear to be an absolutely essential constituent. Besides these there are mineral salts of considerable nutritive importance, though small in quantity. These, with the kreatine and kreatinine, are the chief constituents of beef-tea properly so-called, and will be further treated when I come to that preparation. At present it is sufficient to keep in view the fact that these juices are essential to complete the nutritive value of animal food. FOOTNOTES: