428 INTERNAL SECRETION 



in the liver and accumulates there as reserve material. It is 

 probable that, when the supply of carbohydrates is deficient, the 

 formation of glycogen from albumin also takes place in the livei ; 

 and here, also, the conversion of glycogen into the form in which 

 it is used by the tissues, namely, grape-sugar, takes place. The 

 sugar is withdrawn by the organs from the blood and is in part 

 employed directly in the performance of function ; in part, and 

 in the muscles more particularly, it is converted into glycogen. 

 The process of converting dextrose into a colloid polysaccharide, 

 of condensing the glycogen, and of again converting it into sugar, 

 is the common reversible function of the cells. 



The sugar contents of the blood are dependent upon the 

 amount of sugar formed in the liver. According to Chauveau 

 and Kaufmann, this process is regulated and controlled by the 

 nervous system. These authors believe that two nervous centres 

 exist, one in the medulla oblongata and one in the cervical spinal 

 cord, and that by means of the centrifugal nerves contained in 

 the sympathetic, these regulate the formation of sugar, one centre 

 exercising an inhibitory, the other a direct stimulatory influence 

 upon the sugar production. According to the original theory of 

 these authors, the nervous impulses are first conveyed to the pan- 

 creas, w 7 hence they pass by way of the nerves to the liver, and 

 there bring about changes in the sugar production. Taking into 

 account the many facts which point to a chemical correlation, 

 these authors modified their view to this extent, that they ascribed 

 to the pancreas an internal secretion influencing the liver, which 

 was conveyed to the liver by the agency of the blood-stream. 

 The production of the secretion they believed to be under the 

 control of the nervous system. 



Regarded in the light of our present knowledge, the theory 

 of Chauveau. and Kaufmann signifies that the influence of the 

 internal secretion of the pancreas is exercised directly upon the 

 liver in part only; its main influence is directed to the nerve 

 centres which control the sugar production, the effect upon the 

 stimulatory centre being inhibitory and the effect upon the in- 

 hibitory centre stimulatory. In this way, a two-fold hindrance 

 to the formation of sugar in the liver is effected by the pancreas 

 with the aid of the nervous system. The suppression of the in- 

 ternal secretion of the pancreas not only abolishes inhibition, but 

 it also relieves the check upon stimulation, and, in consequence, 

 a pronounced glycosuria make its appearance. The suppression 

 of inhibition appears, however, to be the decisive factor ; for 

 Hedon and Kaufmann discovered that the hyperglycaemia, or 

 rather the glycosuria, of pancreatic diabetes is by no means 

 maximal and may be increased by puncture of the floor of the 

 fourth ventricle, in other words, by irritation of the stimulatory 

 centre. According to this theory, then, pancreatic diabetes con- 

 sists in an increase in the sugar formation brought about by a 



