others were reduced to a mere husk, while others again were in various states between these two extremes. The whole contents of the stomach exhibited decidedly acid properties; but the litmus paper recovered its blue colour again almost instantly on exposure to the air. They coagulated milk completely, but yielded no trace of an albuminous principle.

Phenomena of Digestion in the Tench and Mackerel.-The contents of the stomach and upper intestines of the tench were examined immediately after death. As, however, the animal had been previously kept for a considerable time in an unnatural state, the phenomena observed were not so satisfactory as could have been wished. The contents of the stomach and upper portion of the intestines consisted of little more than a yellowish glairy fluid, which seemed to be bile; and the small portion of alimentary matter present appeared to be unnatural, and little capable of being acted upon by the digestive powers. No traces of an albuminous principle were, therefore, discoverable, nor indeed could be expected to exist in the stomach, or the upper portions of the alimentary canal. The mackerel, whose digestive organs were the subject of examination, had just arrived from the coast where it had been caught the day before. The stomach was nearly filled with a whitish grumous mass, in which the undigested bony remains of some small fish were distinctly visible. This mass very faintly reddened litmus; and, by the assistance of heat, coagulated milk. It underwent a sort of partial coagulation by the acetic and other acids, especially when heat was applied; but no traces of albuminous matter could be perceived in it.

Phenomena of Chymification.-The examinations of chyme have not been numerous. Dr. Marcet has published a brief account of the chyme of the turkey. I have myself examined the chymes of several different animals: some of the most important of these examinations I shall detail at length; the results of others will be only mentioned. In these examinations my chief object has been to ascertain if the chyme exhibited any traces of the albuminous contents of the blood.

Comparative Examination of the Contents of the Duodena of two Dogs, one of which had been fed on vegetable Food, the other on animal Food only.*-The chymous mass from vegetable food (principally bread) was composed of a semifluid, opaque, yellowish white part, containing another portion of a similar colour, but firmer consistence, mixed with it. Its specific gravity was 1·056. It showed no traces of a free acid, or alkali; but coagulated milk completely, when assisted by a gentle heat.

For the opportunity of making these examinations, as well as those of the chyle afterwards related, I am indebted to the kindness of Mr. Astley Cooper, who, wishing to ascertain the properties of these substances, when preparing his lectures for the Royal College of Surgeons, upwards of four years ago, obligingly furnished me with the materials for making the requisite experiments.

That from animal food was more thick and viscid than that from vegetable food, and its colour was more inclining to red. Its sp. gr. was 1:022. It showed no traces of a free acid, or alkali, nor did it coagulate milk even when assisted by the most favourable circumstances.

On being subjected to analysis, these two specimens were found to consist of

Water

Chyme from ve- Chyme from getable food. animal food. 80:01:

Gastric principle, united with the alimentary matters, and apparently constituting. the chyme, mixed with excrementitious matter...

Albuminous matter, partly consisting of fibrin, derived from the flesh on which the animal had been fed.

86.5

These results were obtained as follows: Water-The quantity of water present was ascertained by evaporating to dryness a known weight of each of the specimens upon a water-bath.

Chymous Principle, &c.--The proportion of this was obtained by adding acetic acid to a known quantity of the mass, and boiling them together for some time. The solid result thus obtained was then collected and dried as before. It consisted partly of a precipitate composed of the digested alimentary matter apparently combined with the gastric principle,* and partly of undissolved and excrementitious alimentary matter. dered it, therefore, as the chyme in which the albuminous principle was not yet so completely formed, or developed, as to be recognized, mixed with excrementitious matter.

Albuminous Matter, &c.-After the above had been removed by filtration, prussiate of potash was added to the acetic solution, which, in the chyme from vegetable food, produced no precipitate, indicating the absence of albumen; but in the chyme from animal food, a copious one. The albuminous matter present in the latter, appears to have been partly derived from the flesh on which the animal had been fed.

Biliary Principle.- Both chymes were found to contain this principle. It was separated by digesting alcohol on the dried residuum of the chyme. This took up the biliary principle,

* The nature of the gastric fluids, and particularly of the gastric juice, or principle, will be more fully considered in a subsequent part of this paper.

which was then obtained by driving off the alcohol. It possessed all the usual properties of this principle, except that it appeared to be less easily miscible with water than in its natural state, and to approach more nearly to the nature of a resin, or adipocire, changes probably induced in it, partly at least, by the action of the alcohol.

Vegetable Gluten?-The chyme from vegetable food, which consisted of bread, yielded a portion of a principle soluble in acetic acid, and not precipitable by prussiate of potash nor ammonia. Hence it was not albumen. It was precipitated by solution of potash, and possessed some other properties analogous to vegetable gluten.

Saline Matters.-The salts were obtained by incineration, and consisted chiefly of the muriates, sulphates, and phosphates, as is usual in animal matters.

Insoluble Residuum.-This consisted chiefly in the vegetable chyme of hairs, &c. in the animal chyme, partly of tendinous fibres.

Such is a brief account of these two varieties of what is usually denominated chyme, and as connected with this subject, I shall add here, by way of contrast, a tabular view of the properties of the alimentary matters taken from different portions of two other dogs which had been similarly fed. These various specimens of alimentary matters were treated with the same general views, and consequently nearly in the same manner, as the two varieties of chyme above described, and the results were as follow:

VEGETABLE FOOD.

ANIMAL FOOD.

1. Chymous Mass from Duo- 1. Chymous Mass from Duo

ANIMAL FOOD.

E. Same as in the cœcum above-mentioned.

F. Salts, nearly as above. Only some traces of an alkaline phosphate were observed.

G. Insoluble residuum, a flaky matter in very minute quantity.

4. From the Rectum. Consisted of firm scybala, of a dark brown colour inclining to chocolate. Smell very foetid. Milk was coagulated by the water in which it had been diffused.

A. Water, quantity not ascertained.

B. Combination, or mixture of altered alimentary matters in much greater excess than in either of the other specimens, with some mucus; insoluble in acetic acid, and constituting the chief bulk of the fæces.

C. Albuminous matter, none. D. Biliary principle, more considerable than in the vegetable fæces, and almost entirely changed to a perfectly resinouslike substance.

E. Vegetable gluten? none; but contained a principle similar to that in the cœcum and colon.

F. Salts, nearly as before. G. Insoluble residuum, consisting chiefly of hairs.

Examination of the Contents of the Duodenum of the Ox.This had been kept for some time before examination, and appeared to contain an unusually large proportion of bile. Its colour was greenish, and it was of a ropy consistence, apparently holding suspended in it some solid matters, which, after a