Page:Proceedings of the Royal Society of London Vol 1.djvu/472

Rh they have been encouraged, there are few commons, no hedges, no shepherds, no dogs to attend the ﬂocks; and the fences of wood and stone are not suﬂicient to prevent active sheep from breaking pasture, to the great destruction of adjacent crops.

The advantage. however, in this respect, is counterbalanced by a corresponding inconvenience arising from the same source, namely, the great difficulty of driving such cripples to market, at the same time that they are generally not so fat as others, from the greater labour they undergo in gathering their food.

These objections are indeed such, that since the introduction of Merinoes, which are equally gregarious, quiet, and orderly, in addition to the strong recommendation of their ﬂeeces, the ancon breed appears in danger of becoming wholly extinct; so that the author had some diﬂiculty in procuring one in Boston to be dissected, for the purpose of sending a skeleton, which accompanied the letter, and was laid before the Society.

It has long since been observed, that the ﬁrst step in the process of digestion i the conversion of the food into a jelly; but whether this effected by means of the gastric liquor alone, or by a joint operation of other secretions, has not been ascertained. From Mr. Hunter’s experiments, it appeared that the same species of coagulation takes place in the same food admitted into the stomach of a great variety of animals; and that in the calf’s stomach this power resided in the fourth cavity alone; since the mucus taken from the surface of the ﬁrst, second, or third cavitie, had no such effect as rennet, which is prepared by infusion of the inner membrane of the fourth cavity.

- The same inquiry is here pursued by the author, with a view to ascertain more accurately what part it is that possesses this property in the highest degree, by comparison of the effects of rennet prepared from different portions.

By this mode of trial no part of the hog’s stomach was found to coagulate mills, but that near the pylorus, where the gastric glands are situated.

Experiments were next made with rennets prepared from the crop and gizzard of a cock, from the stomach of a shark, the stomach of a salmon, and that of a thornback, all of which had the power of coagulating milk.

Other experiments were afterwards made, with the assistance of Mr. Hatchett and Mr. Brande, on the comparative powers of different parts of the same stomach, and the difference in various species of animals, the chicken, hawk, turkey, and calf.

In a chicken the horny lining of the gizzard gave a ﬁrmer curd