The fluid contained in the lacteal vessels in Mammalia is of a white colour like milk, and is called chyle ; it has a marked saline taste, is slightly alkaline, and has no perceptible odour. I have now before me several specimens of recent chyle collected carefully from the lacteal vessels, before they reach the glands, from the glands themselves, from the vasa efferentia of the glands, and from the thoracic duct. These specimens were taken from a donkey killed for the purpose, seven hours after a full meal of oats and beans. About half a drachm was obtained from the vasa inferentia, and a drachm from the mesenteric glands themselves in watch-glasses; from the vasa efferentia about three drachms were procured in a test-tube, and from the thoracic duct in a phial nearly an ounce. All were of a pure milk-white colour except that from the thoracic duct, which had a slight pink tint. They all jellied spontaneously in from five to ten minutes; that from the vasa infe rentia again liquified in about half an hour, and remained in this state ; on other occasions I have known it retain its solidity. I have also seen the chyle from the glands, and from the vasa efferentia, return to the liquid state after having been coagulated for a short period. I have observed the same occurrence in lymph before and after it had traversed a gland. In about half an hour, with the exception already noticed, these specimens of chyle separated into a kind of serum and clot, the latter form ing far the greater portion, at least four-fifths of whole. This clot, however, on being broken up and pressed, contracted to one twentieth part of its former bulk; both the serum and the clot retaining their white colour. In the specimen obtained from the thoracic duct the pink tint was confined to the clot, and the serum was whitish or whey-coloured. It ought here to be stated that chyle, before it has reached the receptaculum, will not always se parate into a fluid and solid portion, but will remain of the consistency of a soft white jelly, from which, however, by breaking it up, a white fluid may be obtained.
I find great error and confusion in the descriptions hitherto given of the microsco pical appearances of the chyle. Miller and Breschet both state, that the white colour of the chyle depends upon its globules, which they then proceed to describe; they both quote Prevost and Dumas as estimating the diameter of the chyle globule at 1-7199th of an inch, or about half that of the blood glo bule in man. Muller says that in the cat he finds them of the same size as the blood cor puscules, and in the rabbit some of them were larger ; in the calf, the dog, and the goat he found them much smaller than the blood cor puscules of the same animal. Breschet,lithis work on the lymphatic system, published in 1836, acknowledges the unsatisfactory state of our knowledge with respect to the globules of the chyle and lymph. Tiedemann and Gmelin, in their elaborate work on digestion, distinctly state they consider the white colour of the chyle to depend upon fatty particles, which form a sort of emulsion with the serous portion of the chyle. Mr. Gulliver has given by far the most correct description of the microscopical appear ances of the chyle that I have met with ; he is the first who has noticed the extremely minute particles which constitute the characteristic microscopical appearance of the chyle, for the larger globules, noticed by most observers, are found also in the lymph. Mr. Gulliver has not, however, corrected the statement of Bre schet, and others that the white colour of the chyle depends upon these larger globules; but I doubt not lie would acquiesce with me in opinion that the white colour' depends alto gether upon the more minute particles. With these preliminary remarks I shall proceed to describe the microscopic characters of the chyle from my own obervations.
Every one is aware that the lacteals, when not conveying chyle, contain a transparent fluid not to be distinguished by the eye from the lymph of other parts of the system ; to this fluid is added, during the digestion of a meal, myriads of extremely minute parti cles, twenty or thirty times less in size than the lymph or blood globules of the same animal, and which can scarcely be distin guished by a glass of less power than one eighth of an inch focus, upon which un doubtedly the white colour of the chyle de pends; when these particles are very numerous, the chyle is perfectly white and opaque; when less so, it will be whey-coloured or semitrans parent. These particles are peculiar to the
chyle, and I have been in the habit, for the last two years, of calling them the chyle gra nules, in contradistinction to the globules of different kinds which are also found in this fluid. The chyle granules, when allowed to dry on a piece of glass, measure from1-20,000th to 1-10,000th of an inch in diameter, and are larger and more distinct in carnivorous than in graminivorous animals. The most remarkable peculiarity, which I believe I am the first to notice, of these chyle granules, is their con tinual vibratory or oscillatory motions. On viewing under the microscope a drop of chyle taken from the lacteal of a carnivorous animal, and placed between a piece of glass and talc, the motions of the chyle granules will be seen to be so constant and ceaseless, that the observer would al first sight be led to consider the chyle as a moving mass of restless animalcules; but on noticing the limited range, as well as the sameness, and apparent want of object, in these to and fro movements, he will probably feel inclined to attribute them to some unknown attraction and repulsion, influ encing inert and unorganized particles. It is assuredly a striking fact, and one fraught with great interest, that the new molecules on their first introduction into the living system, should possess one of the most conspicuous attributes of vitality, viz. motion.° Mr. Ancell, who has paid great attention to the animal fluids, has frequently examined these moveable granules with me, and is inclined to consider their mo tions, as indicating the first obvious impress of vitality which the new material has received from its association with living matter. Be sides the granules, there exist in the chyle numerous spherical globules colourless and granular on the surface, averaging 1-5000th, but ranging between 1-3000th and 1-7000th of an inch in diameter, resembling in every par ticular the lymph globule, with which they are probably identical. These globules I conceive are not derived from the interior of the intes tine as some have supposed, nor from the glands, as I presume is Mr. Gulliver's opinion, but I would rather say arc formed in the chyle and lymph by the aggregation of similar par ticles, probably fibrinous. Globules of oily or fatty matter are also found in the chyle; these may be readily distinguished by their circular and even outline, by their smooth and apparently flat surfaces, and by the great variety of their size, some being as small as the chyle granule, while others exceed the globule in diameter ; in many respects they resemble the milk globule in appearance. Blood corpuscules will of course be frequently seen mixed with the chyle, as it is exceedingly difficult to collect it free from them. In the chyle the blood cor puscule loses its circular outline, its ordinary flattened form, its concave or cupped surface, and assumes a corrugated or wrinkled appear ance, a spiked or serrated edge ; the blood corpuscules, when thus corrugated, are less in diameter than the surrounding chyle globules, and have frequently been mistaken for them. On examining the blood taken from a living animal after a recent flow of chyle into it, this appearance of the blood corpuscule will also be readily distinguished. The corrugations alluded to on the blood corpuscule may be mistaken for spots on it ; and when the corpus cule is revolving or vibrating, they may even appear like particles moving within it. I was for a short time misled by this deceptive ap pearance into the belief that the chyle granule, when received into the blood, entered the envelope of the blood corpuscule to form its nucleus. This erroneous notion, however, was soon corrected on finding that other fluids pro duced the same appearance in the blood cor puscules. It will be observed then, that I am induced to think that the chyle is never per fectly free from lymph; that in fact the lymph is termed chyle when it is rendered white by the addition of the moveable chyle granules from the interior of the intestine, to which are added from the same source the oily or fatty particles.