520 DIABETES 



part of the brain. Glycosuria results from irritation, not from 

 destruction of the center. Undoubtedly the glycogenic center 

 has an important function in regulating glycogen deposition in 

 the liver. That it exercises this function through nervous 

 impulses passing directly from the brain to the liver, has been 

 conclusively shown by experimentally severing various parts of 

 the nervous system in animals whose diabetic centers have been 

 punctured. If the vagus is cut, stimulation of its central end 

 causes glycosuria, indicating that the afferent impulses travel 

 through this nerve, and glycosuria has been observed in persons 

 with tumors pressing upon the vagus. The efferent impulses 

 pass in the spinal cord from the glycogenic center to the upper 

 thoracic spinal roots, and by the rami communicantes into the 

 lower cervical and upper thoracic sympathetic ganglia ; thence 

 by the splanchnic nerves to the liver. How the nervous im- 

 pulses cause the discharge of sugar is unknown, but possibly it is 

 by some direct stimulation of the cells, as with other secretory 

 impulses. Against this, however, is the fact that atropin, which 

 paralyzes all true secretory nerve-endings, does not prevent gly- 

 cosuria from piqure. Bernard thought that the sugar produc- 

 tion was increased merely by vasodilation, and in favor of this 

 view is the fact that a fall of blood pressure decreases or pre- 

 vents the glycosuria. 



In man, glycosuria may result from injuries to the head, pre- 

 sumably because of irritation or stimulation of the glycogenic 

 center. In many nervous diseases more or less transient glyco- 

 suria may occur, and an existing glycosuria may be augmented 

 by nervous stimuli. Administration of thyroid extract, and 

 exophthalmic goiter, may cause glycosuria, presumably from 

 nervous stimulation. Undoubtedly, many of the drugs that 

 cause glycosuria do so through their stimulation of this center. 



3. DRUG GLYCOSURIA 



A. Phlorhisin "Diabetes." 1 This is by far the best 

 known and most studied instance of glycosuria produced by the 

 action of drugs, and offers many points of particular interest. 

 Phlorhizin is a glucoside, obtained from the bark of apple and 

 pear trees, which may be split into dextrose and phloretin, the 

 latter causing the characteristic glycosuric effects. When given 

 by mouth or subcutaneously (the usual dose for dogs is 1 gram 

 per kilo, by mouth, and 0.3 to 0.5 gram subcutaneously), it 



^eeLusk, Zeit. f. Biol., 1901 (42), 31; Cramer, Ergebnisse der Physiol., 

 1902 (1), 877. 



