CH. XXXV.] THE LIVER AND FAT METABOLISM 541 



the blood ; if the phloridzin is directly injected into one renal artery, 

 sugar rapidly appears in the secretion of that kidney ; some explain 

 this by supposing that the sugar is formed within the kidney cells 

 from some substance in the blood, possibly protein ; whereas others 

 consider that the kidney is rendered so permeable to sugar, that the 

 percentage in the blood is kept at a low figure. This view is sup- 

 ported by Underbill's recent work : he has shown that in dogs and 

 rabbits, if the renal structures are ligatured, or the kidney injured 

 by sodium tartrate, the secretion of urine ceases, and after the 

 administration of phloridzin, the sugar in the blood rises consider- 

 ably over the normal. 



(4) By administration of adrenaline. This drug also produces a 

 diabetic condition, but in this case there is excess of sugar in the 

 blood also. Recent research indicates that adrenaline produces an 

 increased discharge of sugar from the liver, and that under normal 

 conditions this is regulated by an antagonistic hormone present 

 in the internal secretion of the pancreas. 



Glycogenolytic Nerves. The disappearance of glycogen from 

 the liver cells after the stimulation of the splanchnic nerves can 

 be seen histologically. This is due to a direct influence of the nerves 

 on the liver cells, for the effect is obtained after the circulation is 

 stopped by ligature of the aorta and portal vein. 



The most complete work on this subject is that by J. J. R Macleod, 

 who finds that the glycogenolytic fibres (the action of which is to 

 increase the sugar in the blood at the expense of the hepatic glycogen) 

 are demonstrable with certainty only in the case of the greater 

 splanchnic nerves. If it occurs as the result of vagus stimulation 

 (as Bernard stated), it is due to the asphyxia which is produced ; if 

 precautions are taken to prevent asphyxia, no increase of the 

 blood sugar is found. In asphyxia it is increase of carbonic acid, 

 and not loss of oxygen, which produces the glycosuric condition, and 

 the former gas probably acts directly on the liver cells themselves. 



The Liver and Fat Metabolism. 



The work of Leathes, Hartley, and others has shown 

 that the liver has an important use in the preparation of fats for 

 their final disintegration into carbonic acid and water. The fat 

 stored in adipose tissue must first be transported into the blood- 

 stream ; the lipase found in connective tissue liberates the glycerin 

 and fatty acids, and thus renders such transportation possible. It 

 is first taken to the liver, where it can be easily detected, but not in 

 other organs, and the rupture of the long carbon chains of the fatty 

 acid begins: it is first desaturated and then broken up into lower 

 fatty acids such as caproic and butyric. The unsaturated products 



