238 



PKODUCTION OF 



remain at the place of its formation. It is constantly absorbed by the 

 blood traversing the capillaries of the organ, and carried away in the 

 current of the circulation. This is shown by the fact that not only the 

 liver tissue, but also the blood of the hepatic vein contains glucose in 

 appreciable quantity, although it may not exist in the portal blood by 

 which the organ is supplied. As the blood accordingly, before its en- 

 trance into the liver, in these cases, is destitute of sugar, and yet con- 

 tains this substance after its passage through the organ, it must acquire 

 its saccharine ingredients by the absorption of glucose in the liver 

 itself. Bernard has shown 1 that if two specimens, of portal and hepatic 

 blood, be taken from the same dog, when in a fasting condition or after 

 an exclusive diet of animal food, the former will show no trace of sugar, 

 while the latter will be distinctly saccharine. Lehmamr has obtained 

 similar results by experimenting upon both dogs and horses. In these 

 animals, nourished with vegetable matters, glucose was found in the 

 blood of the portal vein, though often in very small quantities. In 

 dogs, when under a diet of animal food, the portal blood contained no 

 glucose, while this substance was present in the blood of the hepatic 

 vein. The following table gives the results of Lehmann's experiments : 



QUANTITY OF GLUCOSE IN THE BLOOD OF THE HEPATIC VEIN. AS COMPARED WITH 



THAT OF THE PORTAL 



Glucose, accordingly, although constantly produced in the liver, does 

 not accumulate in the organ during life, owing to its being absorbed 

 by the blood, and carried away nearly as rapidly as it is formed. It is 

 only after death, when the circulation has come to an end and the trans- 

 formation of glycogen still goes on for a time, that the proportion of 

 glucose in the liver tissue becomes notably increased. The circulation 

 of blood through the organ, so. long as it continues, acts like an artificial 

 watery injection of the hepatic vessels, and extracts from its substance 

 the sugar which has been produced at the expense of the glycogen. 



1 Lecjons de Physiologic Bxperimentale. Paris, 1855, p. 265, 469. 



2 Comptes Kendus de 1* Academie des Sciences. Paris, 1855. Tome xi. p. 585. 



