Uric acid exists in the urine of the carnivora, but the quantity is small compared with the urea. Herbivora excrete, mostly, hippuric acid (benzoyl-glycocoll,
| CH2 |  | NHC, H5O |  |
| COOH |
The analysis of the lion’s dung gave the following results:—
Per cent. | ||
| Water | 59 | ·2 |
| Ash | 21 | ·1 |
| Lime (CaO) | 10 | ·3 |
| Phosphates (P2O5) | 10 | ·67 |
| Organic matter | 19 | ·7 |
Dog dung contains some non-volatile bases of the purine group, such as xanthin (C5H4N4O2) and guanin (C5H5N5O), but the action of these bodies in the bate, has not been studied. It is also extremely probable that these and similar bodies are formed during the bating by a process of auto-digestion of various proteids.[24] The quantity of fat in dry puer, amounts to 10–11 per cent. Cholesterol was present.[25] Part of the fat is in the form of lime and magnesia soaps, but part in the form of an emulsion, which probably plays an important part in the puering process. The function of the fatty constituents of puer is one of the problems on which further research is necessary.
The colouring matters of the puer are nearly all derived from bile products. Most of them are found in the petroleum extract, which contains far more of the colouring matters than the chloroform extract.
The following bile colouring matters have been prepared by Merck, of Darmstadt: bilihumin, biliprasin, bilirubin, bilifuscin, biliverdin.[26] So far as has been ascertained by the author, their effect in the bating is nil, but, in so far as they impart colour to the pelt, they are detrimental.
Experiments on the action of bile are given in the paper reprinted in Chapter [VI].