400 PROCESSES INFERRED FROM DIRECT OBSERVATION 



to the passage of sugar into the urine provided that the sugar in the 

 blood does not much exceed the normal concentration of 0.10 to 0.15 

 per cent. After treatment with phloridzin, however, this barrier breaks 

 down. The normal sugar-content is drained out of the blood, and the 

 liver and muscles, in the endeavor to restore the normal equilibrium 

 between Glycogen and Glucose, release glucose continuously to the 

 blood, so that the ultimate result is the drainage of the carbohydrate 

 reserves of the body. That the effect is a purely local one upon the 

 epithelium of the kidneys is shown by the fact that if the phloridzin 

 be supplied only to one kidney by perfusion into the corresponding 

 renal artery, that kidney, but not the other, will eliminate glucose. 

 It has been supposed that phloridzin, being a glucoside, acts as a carrier 

 of glucose across the kidney-epithelium, liberating glucose on the one 

 side and combining with it upon the other, but of this we have no 

 definite proof. 



Yet again, glycosuria may result, temporarily, from an excessive 

 ingestion of carbohydrates, and particularly of sugars. This form 

 of glycosuria, known as Alimentary Glycosuria is not serious unless, 

 indeed, it occurs too readily, when it may indicate a slight or incipient 

 diabetes. It is stated by Gushing that alimentary glycosuria tends 

 especially to occur in conditions of Hyperpituitarism or overactivity of 

 the pituitary gland, of which condition, in fact, he considers a readily 

 elicited alimentary glycosuria to afford confirmatory diagnosis. In the 

 opposite condition of Hypopituitarism he finds, on the contrary, an 

 extraordinary tolerance for ingested sugars and alimentary glycosuria 

 fails to appear 'after a dosage of glucose or levulose which, in normal 

 individuals, would inevitably be followed by an excretion of sugar in 

 the urine. Other observers, while confirming Cushing's observation 

 that pituitary disease is accompanied by disturbances in the carbohy- 

 drate-tolerance, do not concur with him in his view of the relationship 

 of the disturbance to hyper- or hypo-functioning of the pituitary gland. 

 It must be recollected in this connection, however, that our means of 

 distinguishing between hyper- and hypo-activity of the pituitary gland 

 are rendered very imperfect by the fact that the physical effects of 

 previous hyperactivity of the pituitary body persist, and may in fact 

 constitute the most prominent symptoms, long after the condition has 

 passed into one of deficient activity of the gland. 



The possible involvement of the nervous system in the etiology of 

 ^jt diabetic conditions was very strikingly brought into prominence by the 

 discovery of Claude Bernard in 1854 that injury of a certain area in 

 the medulla oblongata induced a transitory but severe glycosuria. 

 The particular area concerned lies between the level of the origins of 

 the auditory nerves and the vagi. The Diabetic Puncture is most suc- 

 cessful in animals that have been well fed with carbohydrates and may 

 fail in ill-nourished animals. The immediate cause of the excretion of 

 sugar which follows this operation is a pronounced Glucohemia, the 

 sugar in the blood rising from the normal level of 0.10 or 0.15 per cent. 



