85. The experiment of Sir B. Brodie, as above related, was repeated by M. Majendie upon adult animals. He found that few of the subjects survived the operation, but that in two cases, wherein they outlived the experiment for several days, white chyle was formed, and frccal matter produced, although not of the usual colour. The animals had not, however, become tinged, as in the parallel experiment of Sir B. Brodie, in which they were deeply jaundiced, the tunica conjunctiva being yellow, and the urine loaded with bile. Results, so contradictory to each other, are certainly very perplexing, and we are, therefore, much indebted to Mr. Herbert Mayo for the important weight of evidence which he has thrown into the scale of the English physiologist. The following are the experiments which agree in their results with those of Sir B. Brodie: -

"The ductus communis choledochus was tied in three cats, each about four months old, which had fasted for twenty-four hours previously. They each took food after the operation, which they threw up; but they afterwards again took food, consisting of milk and raw or boiled meat, and continued to eat occasionally with a natural appetite.

"One of these animals was killed between five and six hours after the duct had been tied. The stomach contained a full meal of meat, consisting in part of morsels, which were softened by the action of the gastric juice, but had undergone no further alteration, in part of a pulpy mass of a reddish-grey colour, in part of a brownish-grey viscid liquid, in which innumerable small globules of oil floated. The small intestines were perfectly empty.

"The second died within fifty hours after the experiment. The stomach contained a small quantity of half-digested food; the small intestines contained scarcely a trace of a greyish semifluid substance, which here and there admitted of being scraped from the villous surface.

"The third was killed three days after the operation. The stomach contained half-digested food; the small intestines contained a quantity of greyish viscid liquid, very like the liquid contents of the stomach. The great intestines, in this and the preceding instance, were distended with a greyish, tenacious, and highly offensive semi-fluid matter.

"An adult dog, in which the duct had been tied, was found dead on the second morning of the experiment. The mucous membrane of the stomach and bowels was inflamed. The stomach contained water only; the small intestines held a quantity of yellowish soapy liquid.

"Finally, the duct was tied in two young dogs, which had fasted for twenty-four hours; one died, the second was killed about forty-eight hours after the operation. Both had eaten boiled flesh, and had taken milk. In the first, the stomach contained half-digested food; and the small intestines contained a quantity of grey liquid, separate from a viscid ropy material that adhered to the villous surface. In the second, the stomach contained a frothy mucus only; but the small intestine was moderately distended with a quantity of yellowish liquid.

"The animals which were killed were immediately examined; those which died were examined from four to five hours afterwards. In each case the duct was found to have been accurately secured; the gall-bladder and gall-duct were distended with bile; there was no trace whatever of chyle in the lacteal vessels1" 86. In the few authenticated cases of the total obliteration of the duct, the emaciation has been extreme, and the circumstance of the patient having lived a few weeks or months, under such circumstances, only proves that nutrition may take place, to some extent, without any chyle being formed. In the above experiments of Sir B. Brodie, it appeared that the more fluid parts of the chyme had been absorbed; and probably this would have been sufficient to maintain life for a limited period, especially where but little exhaustion had been occasioned by exercise. We know that nutritive glys-ters will afford support, and yet we are quite certain that no chyle can be formed under such circumstances. Sir E. Home has related the case of a child in which no gall-ducts existed.

The child did not live long, but it appears to have died rather of a marasmus than of any intestinal affection; and from this fact he concludes, that one of the offices of the bile is that of converting mucus, or the refuse of the chyle as it passes into the colon, into fat, which is absorbed and diffused over the system. I have already offered an objection to this theory (25).

1 "Mayo's Outlines of Physiology," Appendix.

87. When perfectly-formed chyle, as that obtained from the thoracic duct, is chemically examined, it will present a difference in composition, according to the nature of the aliment from which it was elaborated. If the animal has eaten substances of a fatty nature, the chyle will be found milky white, a little heavier than distilled water, with a strong and peculiar odour, and a saline and sensibly alkaline taste; but if the food should not have contained fat, it will be opaline and almost transparent. Very shortly after chyle is ex-10 tracted from the living animal, it becomes firm, and almost solid: it then gradually separates into three distinct parts; the one solid, which remains at the bottom of the vessel, the second liquid, and a third that forms a very thin layer at the surface. The chyle at the same time assumes a rose colour. Of the three parts into which chyle thus spontaneously resolves itself, that on the surface, of an opaque white, and which imparts to the fluid the appearance of milk 1, is a fatty body; the solid part, or coagulum, seems to be an intermediate substance between albumen and fibrin, for it unites several properties which are common to the two: it wants the fibrous texture as well as the strength and elasticity of the fibrin of the blood; it is also more readily and completely dissolved by caustic potass.

The liquid part of chyle resembles the serum of the blood. The proportion, however, of these several parts varies according to the nature of the food. There are species of chyle, such as that from sugar, which contain very little albuminous fibrin; others, such as that from flesh, contain more. The fatty part is very abundant where the food has contained grease or oil, while there is scarcely any under other circumstances. Dr. Marcet instituted a series of experiments upon the chyle, with a view of comparing that produced by vegetable and animal food in the same kind of animal, for which purpose he procured it from the thoracic duct of dogs; in all essential points his results agree with those of Vauquelin. The vegetable chyle generally bore less resemblance to blood than that derived from animal food; the latter was more disposed to become putrid, and upon the addition of potass, it evolved a quantity of ammonia, which was not the case with the vegetable chyle, while the oily matter was only found in the animal chyle. The two species were of the same specific gravity, and contained the same weight of saline matter, but the solid residuum of the animal chyle, as obtained by evaporation, was considerably greater than from the vegetable chyle.

When they were both submitted to destructive distillation, the vegetable chyle produced three times as much carbon as the animal chyle, whence we may conclude, that the latter contains a much greater proportion of hydrogen and nitrogen. Dr. Prout has also given us the results of a comparative series of experiments upon the same subject, and although upon the whole he found less difference between the two kinds of chyle than had been noticed by Dr. Marcet, yet the difference was sufficiently distinct and satisfactory.

1 The comparison which has been established between chyle and milk has no real foundation; for the former contains nothing which agrees exactly with the constituents of the latter. There is also this curious fact, that in the milk traces of certain vegetable principles may be frequently detected; in the chyle this never occurs.