M. Alvaro Reynoso considered that the sugar was destroyed in the healthy organism by respiration, basing it upon what he considered a proved fact that sugar was contained in the blood before its passage through the lungs, but that after that none was found. Diabetes, according to this theory, depends upon deficient respiration, he therefore advocated a stimulant plan of treatment so as to increase the respiratory function.

We now come to a period when the chemical prigin and theories based upon it ceased to be urged, and its origin from nerve lesions to be advocated. For this change we are entirely indebted to M. Claude Bernard, who in Archives Generates de Medecin, 1848, announced the remarkable fact "that sugar was formed in the liver as a normal process in all animals, and that this formation occurred independently of diet, in carnivorous, as well as in herbivorous animals, and that its production was confined to the liver. He showed also that lesions of the nerve centres caused sugar to appear in the urine; by wounding the floor of the fourth ventricle he could produce temporarily sugar in the urine from disturbance of the vaso-motor nerves, and so causing an acceleration of the hepatic circulation. In 1857 he discovered in the liver the matter from which the sugar was formed calling it Glycogenic matter (the Amyloid matter of Pavy). He seemed to have based his theory upon so secure a foundation that there did not appear to be a shadow of doubt as to its truth. Considering, therefore, diabetes to arise from a natural and physiological function of the liver, either from direct irritation or, indirectly, from irritation of the nerves (for he has made known to us a nervous form of diabetes), the treatment was recommended in accordance with this theory, at one time sedative, at another by means capable of acting upon the nervous system, as a seton to the nape of the neck, Bromide of Potassium, Electricity, etc.

This theory of diabetes by Bernard was considered an established fact until the publication of Dr. Pavy's book on the Nature and Treatment of Diabetes in 1862, who denied the power of the liver to form sugar, and considered the formation of this principle as a postmortem result, the nervous system during life preventing its formation. M. Schiff corroborated Dr. Pavy's experiments and a new theory was formed by them of Diabetes which has been called "The theory of Ferments." According to this the Glycogenitic matter, called by Dr. Pavy Amyloid matter, contained in the liver is changed into sugar by the action of a substance analogous to "diastase;" this substance, according to Dr. Pavy, always exists, but is prevented from acting during life by nervous influence; but immediately after death on the withdrawal of nervous influence its action takes place, sugar is thus formed and hence diabetes. Schiff denies the existence of diastase in the liver in its normal state; he considers that it is formed after death and not only in the hepatic blood but also in the blood of the general circulation. According to him, the liver is the centre of the diabetic phenomenon, viz. the formation of sugar, but it is a passive centre, the ferment, or diastase formed in any part of the circulation becoming efficacious in the liver; indeed in order to form the ferment, Schiff con-sidered it was only necessary to put an obstacle in the way of the general circulation, thus he put a ligature round the arm of a man whose urine gave no signs of sugar, he tightened the ligature so as to produce almost complete paralysis of motion and sensibility, the urine voided half an hour after gave decided evidence of the presence of sugar. The augmentation of the ferment has not been demonstrated any more than the ferment itself; further, there are cases of disturbance of circulation without fever in which sugar does not occur in the urine, such as heart affections, congestion of lungs, etc. Schiff proved by experiment that excess of sugar in the blood arises from some modification of the function of the liver; he extirpated the liver of frogs and on examining their blood three weeks after found no sugar. It seems proved by this experiment that pricking the floor of the 4th ventricle does not produce sugar in the blood without the intervention of the liver, and in fact that the liver is the organ by which sugar is formed; he also showed, as M. Claude Bernard had done before, by tying portions of the liver in frogs previously rendered Glycosuric, that the quantity of sugar in the urine diminished in proportion to the diminution of the volume of the liver; hereby confirming the view that the liver is the organ through which Glycosuria or Diabetes has its origin. (Trousseau's Clinical Medicine. Vol. 3. Page 517.)

Dr. Flint of New York, the writer of the Physiology of Man, undertook some experiments on animals to endeavour to reconcile the conflicting opinions of M. Cl. Bernard and Dr. Pavy. He says very truly "it is difficult to understand how any observer so well known and accurate as Dr. Pavy could assert positively, as the result of personal examination, that the liver does not contain sugar when examined immediately after its removal from the living animal whilst Cl. Bernard and so many others have demonstrated its presence in large quantities;" yet such was the result of all the experiments of Dr. Pavy, and the same conclusion was arrived at by Dr. McDonnell, Meissner, Saeger, and Schiff. As the result of his experiments there seems to be no doubt that the liver in a living animal contains no sugar, agreeing thus with Dr. Pavy; but he differs from him in this respect, that though no sugar is found in the liver yet it is formed by the liver, being he considers washed away by the blood into the hepatic veins as fast as it is formed; his experiments shew how very quickly after death sugar is formed by the liver. This conclusion was founded on the fact that though only meat was taken as food, yet when an extract was made from the blood of the Portal vein and from the substance of the liver no sugar was found in them, although an extract made from the blood of the Hepatic vein always indicated the presence of sugar. He considered, and I think rightly, that this sugar could only be derived from a sugar-forming function of the liver, for as no sugar is found in the Vena Porta, nor in the liver when examined quickly after death, but is always met with in the hepatic veins, it is impossible to conceive that the sugar is derived from any other source than the liver,* thus establishing Bernard's theory that the liver manufactured sugar,† and that therefore Diabetes may consist of an exaggerated normal function of the liver. We shall enter further upon this subject when we consider the important question, what constitutes Diabetes or in what does Diabetes consist?

* All Physiologists, whose works I have read, admit that sugar is always met with in the hepatic vein, though none be discovered in the Vena Porta.

† This Physiologist fed a well-nourished adult dog for seven days on sheep's heads, then he killed it, and found sugar in the hepatic vein though there was none in the portal vein.