We come now to the important question: What is Diabetes ? or in what does Diabetes consist? It was formerly thought that the office of the liver was only to secrete bile, and then it was difficult to explain its size and characters, more especially in the embryo state; but since its influence in the process of sanguification, and especially its Glycogenitic functions have been discovered, its prominence among the glandular organs (to use the words of Mr. Marshall in his work on Physiology) can be sufficiently accounted for. Besides its influence in the process of sanguification and in secreting bile, later researches have proved that it has two other important functions to perform.

1st. The formation of Glycogenitic or amy-loid matter.

This matter seems to be formed not only from the saccharine and starchy substances taken as food, but also at the expense of the nitrogenised substance of the tissues and organs of the body itself: part of this matter in a healthy subject is being constantly carried off by the hepatic veins and assimilated, while the surplus is stored up for future use. It is allowed by all physiologists that this matter is formed in the liver, not only of animals that feed on sugar and starchy matter but also of those that feed exclusively on flesh. That it is largely formed from the saccharine and amylaceous food is clearly proved by the experiments made by Dr. McDonnell, related in his treatise on the function of the liver,* he says it is surprising, almost incredible, to what a degree and with what rapidity the liver may be increased or diminished in bulk by the administration of particular kinds of food.

So far as this is due to an increased or diminished quantity of amyloid substance stored up in the liver the following table will show:-

Dr. Pavy's experiments corroborate this.

From the above table it is clearly seen how much the amyloid matter is dependent on diet; starch and sugar being the great producers of it.

2nd. The liver, from the amyloid or glycogeni-tic matter, forms an easily assimilated sugar; this in the healthy state is absorbed by the system, so that the amyloid or glycogenitic matter is the intervening stage between the sugar and starch taken as food and the sugar that is to be absorbed by the system in a healthy state. How easily this sugar, compared with other sugars, is assimilated, is shewn by some experiments of Cl. Bernard, He injected under the skin of a rabbit a little more than 7 grains of cane sugar in about one ounce of water, and found decided indications of sugar in the urine: under the same conditions he found he could inject nearly 7 grains of milk sugar, 14½ grains of glucon, 21½ grains of diabetic sugar, and nearly 33 grains of liver sugar, without finding sugar in the urine; hence we see the reason of the reconversion of the amyloid or glycogenitic matter into sugar. No one can doubt this function of the liver after reading the carefully conducted experiments of Dr. Flint.

* Dublin, 1865.

In many cases of Diabetes the sugar in the urine cannot have its origin from the sugar and starch taken as food; for it has occurred when the patient has been absolutely restricted to an animal and fatty diet. Observations made with the greatest care by the Rev. S. Haugh-ton on the phenomena of Diabetes Mellitus, Dublin, 1861, shew that sugar excreted in Diabetes has a double origin, being partly derived from the starch and sugar in the food, and partly from the decomposition of protein substances. He considers that the protein compounds resolve themselves into glucose and urea.

This decomposition probably takes place in health also, as in healthy lymph sugar and urea are always found:* the difference being that in health they are given out as the result of work, whilst in Diabetes without work.

Here I may state the difference I make between Glycosuria and Diabetes: in the former there is sugar in the urine, but unattended by very pronounced general symptoms, such as thirst, very dry skin, great emaciation; in fact the general symptoms are so little complained of that the sugar is very often discovered acti-dently; whilst in Diabetes the sugar in the urine is always accompanied by well marked general symptoms. In the first, the sugar seems to be entirely excreted from the system; whilst in the second, the sugar is retained, and, accumulating in the system, poisons the various tissues and organs, and thus, in proportion to its retention and accumulation, causes danger. Therefore, not Glycosuria only, but also Diabetes may have a two-fold origin, 1st. The sugar and starch taken as food, not being converted into amyloid matter, passes through the liver into the general circulation and is excreted by the kid-neys as sugar; for De Becker has found that if sugar exists in the blood beyond 5 decigrammes in 100 grammes, (the decigramme being equal to about 1½ grains, therefore about 7½ grains in 1550 grains), Glycosuria must necessarily occur, and it must be got rid of by the kidneys. This non-conversion of sugar into amyloid matter seems to have some relation to the rapidity with which starchy matter is converted into sugar; if a too rapid conversion takes place, it, as it were, overtasks the powers of the liver to convert it into amyloid matter (the power of the liver seems to be limited in this respect); the sugar thus passes through the liver and appears in the kidneys. This fact is, I think, proved from the experiments of M. Bouchardat. He gave 4 dogs and 3 rabbits, a mess of starch, having previously mixed it with diastase: in 5 out of 7 he found sugar in the urine. He adds, that he analysed the urine of these animals after starch had been given without diastase; not the least trace of sugar was found. This experiment seems to prove, also, that the power of the liver to convert starch into amyloid matter varies in animals of the same species. It seems also, from the experiments of M. Lecomte, that for cane sugar to be assimilated it must pass through the liver. If a solution of cane sugar be injected into the jugular vein, the sugar ap- . pears in the urine; but if the solution be injected into the vena porta, and so passes through the liver, no sugar appears in the urine.

* Flint's Physiology of Man.

2nd. Glycosuria and Diabetes may arise from an increased production of sugar, beyond what the powers of the system can assimilate, the surplus being carried off by the kidneys.