DIGESTION. 283 



Glycosuria. The facility with which the glycogen of the liver is 

 transformed into sugar would lead to the expectation that this chemical 

 change, under many circumstances, would occur to such an extent that 

 sugar would' be present not only in the hepatic veins,, but in the blood 

 generally. Such is frequently the case; the sugar when in excess in the 

 blood being secreted by the kidneys, and thus appearing in variable quan- 

 tities in the urine (Glycosuria). 



Influence of the Nervous System in producing Glycosuria. 

 Glycosuria may be experimentally produced by puncture of the medulla 

 oblongata in the region of the vaso-motor centre. The better fed the 

 animal the larger is the amount of sugar found in the urine; whereas in 

 the case of a starving animal no sugar appears. It is, therefore, highly 

 probable that the sugar comes from the hepatic glycogeti, since in the one 

 case glycogen is in excess, and in the other it is almost absent. The 

 nature of the influence is uncertain. It may be exercised in dilating the 

 hepatic vessels, or possibly on the liver cells themselves. The whole 

 course of the nervous stimulus cannot be traced to the liver, but at first 

 it passes from the medulla down the spinal cord as far as in rabbits 

 the fourth dorsal vertebra, and thence to the first thoracic ganglion. 



Many other circumstances will cause glycosuria. It has been observed 

 after the administration of various drugs, after the injection of urari, 

 poisoning with carbonic oxide gas, the inhalation of ether, chloroform. 

 etc., the injection of oxygenated blood into the portal venous system. It 

 has been observed in man after injuries to the head, and in the course of 

 various diseases. 



The well-known disease, didbetus mellitus, in which a large quantity 

 of sugar is persistently secreted daily with the urine, has, doubtless, some 

 close relation to the normal glycogenic function of the liver; but the 

 nature of the relationship is at present quite unknown. 



The Intestinal Secretion, or Succus Entericus. On account of 

 the difficulty in isolating the secretion of the glands in the wall of the 

 intestine (Brunner's and Lieberkiihn's) from other secretions poured into 

 the canal (gastric juice, bile, and pancreatic secretion), but little is known 

 regarding the composition of the former fluid (intestinal juice, succus en- 

 tericus). 



It is said to be a yellowish alkaline fluid with a specific gravity of 

 1011, and to contain about 2 -5 per cent, of solid matters (Thiry). 



Functions. The secretion of Brunner's glands is said to be able to 

 convert proteids into peptones, and that of Lieberkuhn's is believed to 

 convert starch into sugar. To these functions of the succus entericus the 

 powers of converting cane into grape sugar, and of turning cane sugar 

 into lactic, and afterward into butyric acid, are added by some 

 physiologists. It also probably contains a milk-curdling ferment (W. 

 Roberts). 



