Saccharine Diabetes (Diabetes Mellitus, Glycosuria, or Inosuria).

This is primarily a disease of the nervous system or liver rather than of the kidneys, yet, as the most prominent symptom is the sweet urine, it may be treated here.

Causes. Its causes are varied, but resolve themselves largely into disorder of the liver or disorder of the brain. One of the most prominent functions of the liver is the formation of glycogen, a principle allied to grape sugar, and passing into it by further oxidation in the blood. This is a constant function of the liver, but in health the resulting sugar is burned up in the circulation and does not appear in the urine. On the contrary, when the supply of oxygen is defective, as in certain diseases of the lungs, the whole of the sugar does not undergo combustion and the excess is excreted by the kidneys. Also in certain forms of enlarged liver the quantity of sugar produced is more than can be disposed of in the natural way, and it appears in the urine. A temporary sweetness of the urine often occurs after a hearty meal on starchy feed, but this is due altogether to the super-abundant supply of the sugar-forming feed, lasts for a few hours only, and has no pathological significance. In many cases of fatal glycosuria the liver is found to be enlarged, or at least congested, and it is found that the disorder can be produced experimentally by agencies which produce an increased circulation through the liver. Thus Bernard produced glycosuria by pricking the oblong medulla at the base of the brain close to the roots of the pneumogastric nerve, which happens to be also the nerve center (vasomotor) which presides over the contractions of the minute blood vessels. The pricking and irritation of this center leads to congestion of the liver and the excessive production of sugar. Irritation carried to this point through the pneumogastric nerve causes saccharine urine, and, in keeping with this, disease of the pancreas has been found in this malady. The complete removal of the pancreas, however, determines glycosuria, the organ having in health an inhibitive action on sugar production by the liver. The same result follows the reflection of irritation from other sources, as from different ganglia (corpora striata, optic thalami, pons, cerebellum, cerebrum) of the brain. Similarly it is induced by interruption of the nervous control along the vasomotor tracts, as in destruction of the upper or lower cervical sympathetic ganglion, by cutting the nervous branch connecting these two, in injury to the spinal marrow in the interval between the brain and the second or fourth dorsal vertebra, or in disease of the celiac plexus, which directly presides over the liver. Certain chemical poisons also cause saccharine urine, notably woorara, strychnia, morphia, phosphoric acid, alcohol, ether, quinia, chloroform, ammonia, arsenic, and phlorizin.

Source: Diseases of the Horse