240 PRODUCTION OF 



Accumulation of Glucose in the Blood, and its discharge by the Urine. 

 The sugar formed from the glycogen of the liver, and discharged little 

 by little into the circulation, is not usually recognizable at a distance 

 from the organ, owing to the changes which it undergoes in the blood. 

 But under certain conditions its quantity, or the rapidity of its dis- 

 charge by the liver, may be increased ; so that, its decomposition no 

 longer keeping pace with its production, it is diffused to a greater dis- 

 tance from the point of its origin. Bernard has observed this to take 

 place, in an appreciable degree, during ordinary digestion. In this pro- 

 cess, the circulation through the liver being increased in intensity, after 

 a time the glucose derived from its substance may become perceptible 

 in small quantity beyond the lungs, and traces of it may appear in the 

 arterial blood. At the same time its alteration continues to be effected, 

 so that the venous blood, after passing through the capillaries of the 

 general system, is no longer saccharine. This condition lasts but for a 

 short time. As the digestive process comes to an end, and the hepatic 

 circulation returns to its ordinary standard of activity, the glucose 

 which it supplies to the blood is again reduced to such a proportion, that 

 it disappears altogether from the vascular system beyond the right side 

 of the heart. 



If, however, from any cause, the quantity of glucose in the blood of 

 the general circulation be increased beyond a certain proportion, it then 

 fails to be completely decomposed or assimilated, and a part of it is dis- 

 charged by the kidneys. Under these circumstances the urine becomes 

 saccharine, and the animal is placed in a condition of diabetes. The 

 proportion of glucose which the blood must contain, in order that it may 

 be discharged by the kidneys, lias been determined in several instances. 

 Yon Becker found 1 that in rabbits, if glucose be present in the blood in 

 the proportion of 5 parts per thousand, it passes off by the urine, where 

 it may be distinctly recognized by the copper test ; but if less abundant 

 than this, the indications of its presence in the urine are faint and un- 

 certain. Bernard ascertained, 2 by injecting in the same animal a solu- 

 tion of glucose into the veins, that in general a condition of diabetes 

 was produced when glucose was injected in larger quantity than one part 

 per thousand of the entire bodily weight. The appearance of glucose in 

 the urine is therefore dependent upon the proportion in which it exists 

 in the blood. If its quantity be below a certain point, it is all decom- 

 posed by contact with the ingredients of the blood ; if it be above this 

 point, some of it escapes this change and is then eliminated as an in- 

 gredient of the urine. According to the experiments of Von Becker, a 

 solution of glucose, injected into the jugular vein of the rabbit in suffi- 

 cient quantity, may cause the appearance of sugar in the urine in less 

 than three hours ; but at the end of from six to seven hours the whole 



1 Zeitschrift fiir Wissenschaftliche Zoologie, Band v. p. 176. 



2 LeQons sur les Liquides de 1'Organisme. Paris, 1859, tome ii. p. 73. 



