Occurrence, Etiology. 923 



paratiyely few instances. The reason may lie in the fact that urinary 

 analysis did not receive proper attention in veterinary medicine until 

 quite recently. Interesting eases of diabetes mellitus have been de- 

 scribed by Thiernesse, Rueff, Leblanc, Saint-Cyr, Haubner, Heiss, 

 Dieckerhoff, Frohner, Eber, Schindelka, Eiehhorn, Penberthy, Lind- 

 quist, Lienaux, Fettick, Sendrail & Cuille, Bohl, Kriiger, Preller, Eisen- 

 menger and others. 



Occurrence. Diabetes mellitus is, as a rule, verv rare in 

 domestic animals, dogs being most frequently affected, horses 

 far less often (according to, Frohner, one out of 10,000 dogs 

 is diabetic; according to Eber, one out of every 1,000). Aside 

 from dogs and horses, the disease has been observed only in 

 cattle (Darbas, Girotti) and monkeys (Leblanc), which does 

 not, however, exclude the possibility of its occurring in other 

 animals. 



_Etiology._ There is at present no doubt that diabetes 

 mellitus is etiologically not a uniform disease. It can be pro- 

 duced by certain organic affections of the central nervous sys- 

 tem, of the liver or pancreas, and occasionally occurs inde- 

 pendently of any demonstrable organic disease. Eecent investi- 

 gations indicate that diabetes mellitus often develops on ac- 

 count of a pancreatic anomaly, especially of the islands of 

 Langerhans, which may be demonstrated only with the micro- 

 scope. 



The influence of the central nervous system upon the sugar cleavage 

 in the organism was shown by the well known experiment of CI. Bernard 

 in which it was found that an injury to a certain portion of the 

 medulla oblongata, on the floor of the fourth ventricle near the vagus 

 root ("sugar puncture," "piqure") leads to a transitory glycosuria. 

 Other authors found later that the same takes place after lesions of 

 other portions of the central nervous system (cerebellar worm, cervical 

 cord) or of the cervical sympathetic. The central nervous system 

 exerts its influence exclusively or mainly by the intermediation of the 

 splanchnic nerve, at least the "piqure" does not produce such results 

 after the nerve is divided. The glycosuria occurs here evidently by 

 the irritation of the puncture, causing the liver to discharge its glycogen 

 suddenly so that the blood becomes charged with grape sugar. This 

 agrees with some observations in diabetic human patients in whom 

 these portions of the nervous system, the abdominal sympathetic, and 

 principally the solar ganglion or the coeliac plexus were found altered. 

 All these experiences indicate that certain parts of the central nervous 

 system or of the sympathetic may be concerned in the origin of diabetes 

 mellitus (neurogenic diabetes). 



The liver is an essential factor in the formation of sugar, because 

 in this organ the grape sugar which is ingested with the food or fornied 

 and absorbed during the digestion of carbohydrates is transfornied 

 into glycogen, and thus the blood is kept from being flooded with 

 grape sugar during each period of digestion. For this reason it is 

 possible, in case the function of the liver is disturbed, that a portion 

 of the grape sugar which was absorbed -in the intestinal canal is not 



