36 SECRETION 



It is stated that the juices expressed from muscle and pan- 

 creas have very little glycolytic power when taken separately, 

 but when combined cause a marked disappearance of sugar 

 added to the mixture. It is assumed that the pancreas furnishes 

 an internal secretion necessary to the consumption of sugar 

 by the tissues. Since the effect is not lost by boiling the extracts, 

 the essential body cannot be an enzyme, but is of the nature 

 of hormones. It is said to be formed by the islands of Langer- 

 hans. Injection of paraffin into the ducts of the pancreas 

 gives an atrophy of the ordinary secretion cells only. If a 

 portion of the gland is separated off from the rest and its duct 

 is tied, it undergoes atrophy, leaving only islands of Langerhans 

 and the remains of ducts. If the normal part of the gland is 

 now removed, no glycosuria results, even when dextrose is 

 injected. But a further step in the removal of the atrophied 

 portion gives a typical glycosuria. 



There are observers who do not believe that islet tissue 

 differs essentially from the alveolar tissue, and who assert 

 that during exhaustion of the gland a great part of the alveoli 

 is transformed into islet tissue and restored after rest. Lesions 

 of the pancreas are certainly often found in diabetes, and in 

 certain cases the changes observed were in the islands. In 

 cirrhosis of the liver it has frequently been shown that the 

 pancreas also is affected by the growth of connective tissue. 



Liver. The liver possesses three well-recognized func- 

 tions: (1) It manufactures the product bile, which is partly 

 an excretion and partly a secretion. (2) It is the seat of 

 manufacture of urea, which is passed to the blood and thus 

 to the kidney to be excreted. (3) It forms a prominent store- 

 house for glycogen. 



The amount of bile secreted varies, but for man may be 

 stated to be about 800 c.c. a day. The liver cells which are 

 in relation to the mixed blood of the portal vein and the arterial 

 blood of the hepatic artery are probably continuously active. 

 The bile, stored in the gall-bladder, is ejected intermittently. 

 It has been shown that the quantity of bile formed varies 

 with the quantity and quality of the blood supplied to the 

 liver. Bile salts stimulate liver cells, and all such substances 

 are designated as cholagogncs. 



Stimulation of the spinal cord diminishes the secretion. 



