are suitable when the physician searches for it in such fluids as urine, milk, sweat. Simon's: Add nitric acid to the fluid on a white plate or sheet of writing paper, and green, pink, and other tints play round wherever the acid falls. Pettenkofer's: To some of the fluid, in a tube, add of sulphuric acid and a solution of sugar; a violet red colour appears if bile is present. As sugar and sulphuric acid produce a somewhat similar colour, especially if albumen or oil be present, the test is fallacious. It acts on the cholic acid and not on the pigment, as the same reaction occurs with decolorised bile.

The functions of the Liver are complex and not perfectly understood, but they appear to be-1. To rid the blood of hurtful matter, and-2. To elaborate matters of use in digestion and other nutritive acts. 1. That it is more excrementitious than digestive is suggested by its secretion being constant, like the urine-not occasional, like the gastric juice; it is separated from venous blood like urine-not from arterial, as most truly nutritive fluids are; and by the symptoms of poisoning which its sudden retention in the blood produces, being analogous to those which occur when the lungs or kidneys are interfered with (apnoea and uremia). However, in many instances the retained bile causes no injurious effects; and Budd accounts for those symptoms of poisoning it produces in others, by supposing that it becomes decomposed-just as urea must be changed before any signs of uremic poisoning occur.

Sulphur and colouring matters would seem to be the chief excreta, as all others are re-absorbed, only about 20 grs. daily appearing in fæces, though so great a quantity of bile is secreted. Boerhaave, 150 years ago, thus expressed this fact: "Almost the whole mass of the fluid secreted by the liver is again secerned or drunk up by the absorbing veins from the alimentary and fæcal contents before they arrive at the anus." 2. That it is not merely excrementitious is suggested by its duct always

opening high in the alimentary canal, and was demonstrated by Schwann's experiment; he excluded the bile from the intestines by tying the duct, and then provided for its full excretion by discharging it externally through a fistulous opening. Of 18 dogs thus treated only 2 lived, and in them the duct had established another communication with the intestine. The others died in 2 or 3 weeks emaciation, debility, unsteadiness of gait, and falling off of hairs having occurred, and gradually increased till death. It should not be concealed that similar experiments have obtained somewhat different results, and there are many cases where men have survived many months, though no bile passed through the digestive canals. We have no evidence that it acts chemically on the starch, fat, or nitrogenized portions of our food, save that it checks decomposition and evolution of gas, which occur so readily in jaundice. Out of the body it has been found to arrest alcoholic fermentation and putrefaction of flesh.

It is believed to be purgative by exciting the secretion of mucus, which will be found much more abundant wherever the bile has passed. Ox-gall has been given as a cathartic. Its use in promoting absorption of fat

has been before alluded to. Its influences on the blood may be next mentioned, and they are so important as to earn for the gland the title of blood-refiner. Weber, by examining the rudiments of liver in the chick and in frogs, concluded that in it "a material is separated and accumulated from the blood, out of which the blood corpuscles are formed." The blood of the hepatic vein is said to be richer in white cells than that of porta, a fact advanced to support the theory just stated; but it is, on the contrary, a strong argument that the red-cells are disintegrated, and their hæmatin thrown off as bilepigment, leaving the white cells proportionally more numerous. Lehmann believes the blood loses much fibrin by passing through the liver, being converted into

glycin and taurin, and scarcely appearing in hepatic venous blood. This fact supports the view that fibrin is a compound beyond albumen in the downward course (see p. 115). The chemical changes which occur in the liver are sources of animal heat, and Bernard found the temperature of that in hepatic vein higher than that of porta or aorta. The liver and lungs have been regarded as vicarious in performing the great acts of respiration and calorifaction; and the great size of the former in fœtal life and herbivora, where the action of the lungs is either not developed or exerted in a degree far below that of carnivora, supports the doctrine, which, however, the great size of the gland in the boa and other cold-blooded animals throws doubt on. Two heat-giving materials are generated in the liver-namely, fat, which is found abundantly in the hepatic cells, and sugar.

The Glycogenic Function of the liver was discovered and profoundly investigated in 1848 by Claude Bernard. He found sugar in the liver of carnivora, and still more in herbivora, from the starchy and saccharine nature of their food; but it was present in dogs after they had been fed for eight months on calves' heads and tripe, all vegetable food being excluded. That it is not due to digestive action, but to a power inherent in the liver, is shown by its occurring in animals kept long fasting, and when no trace can be found in the blood of porta or hepatic artery. The fresh liver of the horse contains about 4, man 2, and reptiles about 1 per cent. hepatose, or liver sugar, obeys every test which produces re-actions with grape sugar, and will yield alcohol by fermentation, when injected into the veins. It differs, by so readily undergoing decomposition and never escaping with the urine. The capillaries-or, according to Handfield Jones, the hepatic cells-are the organs which elaborate it; and he regards these cells as not within the ducts, and thus unconnected with the secretion of bile.

The

Dr. Pavy regards the formation of sugar as an occur

rence after the death of the animal, and has performed many experiments to support this view. The matter which is convertible into sugar he calls "the amyloid substance," and assigns it the formula C12 H12 012. In two instances-the liver of a cod and of a rabbit-he found this matter not changed into sugar even many hours after death; but the change usually occurs most rapidly. Brücke, and some English analysts, have demonstrated that urine normally contains sugar; and if so much sugar were formed in the liver as Bernard avers, it would be excreted, and we would be all suffering from diabetes mellitus.

If

Even after the tissue has been washed, and all sugar dissolved out by injecting water, still it will generate sugar if left aside for 24 hours. A maximum amount of sugar is formed about 4 or 5 hours after a meal. starch or other kinds of sugar are taken, they are absorbed by the vena portæ, and changed in the liver into hepatose. From the liver the hepatose is carried to the lungs through the right side of heart, where it can be obtained plentifully; it disappears almost completely in the lungs, for the blood at the left side of the heart scarcely contains a trace. The only vessels from which it is completely absent are those of the chylopoietic viscera, when none had been recently taken with food. Harley has determined the important fact, that alcohol and other stimulants injected into the vena portæ, will excite the liver to so great an increase of its glycogenic function, that sugar will be excreted by the kidneys. Diabetes has been often due to the habitual use of intoxicating liquids. Bernard states that the changes of the sugar in the lung are not simple oxidation and the production of carbonic acid; and Lehmann suggests that it ferments, becomes lactic acid, which, acting on the carbonate of soda in the blood, sets free carbonic acid, and forms lactate of soda. The ferment which is necessary to produce these changes is fibrin, and it has been found that defibrinated blood

Besides

if charged with sugar, may pass through the pulmonary circulation without any loss of sugar. Another necessary condition of the blood is its alkalinity. such offices in connexion with aeration of the blood, Bernard regards sugar as required for the development of the blood-cells.

Another remarkable discovery of Bernard's was the influence of the nervous system on the glycogenic function. If the pneumogastrics be divided, no sugar whatever is formed in the liver. The contrary occurs, and sugar is formed so abundantly, that it passes off by the urine, constituting "an artificial diabetes," when the floor of the 4th ventricle is irritated or injured. Bernard justly supposes that it is secreted by a reflex influence, transmitted from the lungs to the medulla, and thence sent down the spinal cord, section of which checks its formation; whereas the pneumogastrics may be divided below the lungs without any interference, and if they are divided in the neck, galvanizing the upper end will excite the formation of sugar. The effect of the want of due aeration, as in fœtal and very advanced life, during the administration of chloroform, and in all diseases affecting the respiratory organs, will be again referred to, as the latter circumstances are powerful causes of diabetes. During foetal life the placenta performs a glycogenic function. Dr. R. M'Donnell has communicated to the Royal Irish Academy some most important observations, which go to prove that the amyloid substance is but a stage between the ternary and quaternary compounds, and is in progress of assimilation. He has found it in the following situations besides the liver— the placenta, many parts of foetus, muscles and lungs of hybernating animals, and in paralysed muscles. I have much pleasure in referring to his valuable memoirs in the Natural History Review for July, 1860, and that in the Dublin Journal, August, 1859, for an admirable account of the subject.