442 THE HUMAN BODY. 



are known; one in which sugar appears in the urine only 

 when the patient takes carbohydrate foods; the other in 

 which it is still excreted when he takes no such foods, and 

 must therefore form sugar in his Body from substances not at 

 all chemically allied to it. The most probable source of the 

 sugar in the latter case is proteids; since some glycogen is 

 found in the livers of animals fed on proteids only, while fats 

 alone give none of it. In some complex way the proteid mole- 

 cule would appear to split up in the liver into a highly nitro- 

 genized part (urea, or an antecedent of urea) and a non- 

 azotized part, glycogen. On this view the more severe form 

 of diabetes would be due to an increased activity of a normal 

 proteid-decomposing function of the hepatic cells; and 

 sometimes the urea and sugar in the urine of diabetics 

 rise and fall together, thus seeming to indicate a com- 

 munity of origin. Diabetes dependent on carbohydrate 

 food might be produced in several ways. The liver-cells 

 might cease to stop the sugar and, letting it all pass on into 

 the general circulation, suffer it to rise to such a percentage 

 in the blood after a meal, that it attained the proportion in 

 which the kidneys pass it out; or the tissues might cease to 

 use their natural amount of sugar, and this, sent on steadily 

 out of the liver, at last rise in the blood to the point of ex- 

 cretion. Or the liver might transform (into glucose) and 

 pass on its glycogen faster than the other tissues used it, 

 -and so diabetes might arise; but this would only be tem- 

 porary, lasting until the liver stock was used up by the 

 rapid conversion. Artificially we can, in fact, produce 

 diabetes in several of these ways; curari poisoning, for ex- 

 ample, paralyzing the motor nerves, makes the skeletal 

 muscles lie completely at rest, and so diminishes the glyco- 

 gen consumption of the Body and produces diabetes. Car- 

 bon monoxide poisoning produces diabetes also, presumably 

 by checking bodily oxidation. Finally, pricking a certain 

 spot in the medulla oUongata causes a temporary diabetes. 

 This may be due to the fact that the operation injures 

 that part of the vaso-motor centre which controls the mus- 

 cular coat of the hepatic artery; this artery, then dilating, 

 carries so much blood through the liver that an excess of 



