So far as is at present known the unorganised ferments in the dung, besides those which are secreted by the bacteria, are mostly digestive ferments[114] —pepsin, pancreatin, and trypsin—certain quantities of which pass out of the animal’s body in an unchanged condition. Of these, pepsin only acts in an acid solution, and, although fresh bate liquor is faintly acid to litmus, it quickly becomes neutralised by the lime in the skins, so that the action of this ferment can only be limited in extent. Pancreatin will act in a neutral solution, and has, therefore, a considerable effect on the skin.
Some Dung Analyses.
Hen Dung | Dog Dung | Guano | |||
Per Cent. | Per Cent. | Per Cent. | |||
| Moisture | 60·88 | Ca | 43·049 | Urea | 5·00 |
| Organic matter † | 19·22 | Mg | 0·087 | K2SO4 | 7·90 |
| Phosphates | 4·47 | K | 0·302 | NaCl | 5·00 |
| CaCO3 and CaSO4 | 7·85 | Na | 0·438 | (NH4)3PO4 | 5·50 |
| Alkaline salts | 1·09 | Si | 0·004 | (NH4)2O | 0·60 |
| Silica and sand | 6·69 | PO4 | 3·446 | SiO2 | 2·25 |
──── | CO2 | 7·464 | Ca3(PO4)2 | 9·00 | |
100.00 | Cl | 0·037 | MgNH4PO4 | 15·25 | |
| Fe and loss | 0·008 | Ammon. urate | 15·25 | ||
| Organic matter | 14·152 | Organic matter (17 per cent. N) | 41·73 | ||
| † Containing N = ammonia 0·74 | H2O | 31·013 | Moisture | 6·52 | |
───── | ──── | ||||
100·000 | 100·00 | ||||
W. I. Macadam, J.S.C.I., 1888, 80. Viollet, Diction d’Analyses Chim.
The dog dung actually used in a tannery is from animals fed on a more vegetable diet, the one given having an extremely high percentage of lime, no doubt owing to the animal having eaten bones. A dung as brought from the kennels was found to contain:—
| Per Cent. | |
| Mineral matter | 4·679 |
| Organic " | 9·731 |
| Water " | 85·590 |
| ───── | |
| 100·000 |
I find by experiments with the purified ferments that their action is very slow compared with the bate itself. Two portions of the same skin were taken: one of them was treated with a 1 per cent. solution of pepsin acidified with 0·2 per cent. of hydrochloric acid, the other in a bate liquor of dog’s dung; both at a temperature of 40° C. (104° F.). At the end of one hour, the skin in the pepsin solution was considerably “fallen,” but that in the manure solution was bated nearly away, i.e. the greater part of it was dissolved.
A 1 per cent. solution of pancreatin (Merck’s) was found to act far more rapidly than pepsin. At 40° C. in a neutral solution the skin fell rapidly, and the action continued even in the cold. In this experiment it was found that in 15 hours the liquid was swarming with minute bacteria. In order to guard against the influence of bacteria a similar experiment, at the suggestion of Mr. H. R. Procter, of the Yorkshire College, Leeds, was tried with the addition to the pancreatic solution of 1·5 per cent. of chloroform; this prevents the development of bacteria, while it does not interfere with the action of the pancreatin. The skin was reduced as before, but in neither case had it the peculiar touch of a “puered” skin, nor were the characteristics of the leather the same.