38 SECRETION 



a port-wine red color instead of the blue of an ordinary starch 

 reaction. It can in this way be detected in the liver, micro- 

 scopically. The average amount varies between 1.5 to 4 

 per cent, of the weight of the liver. In man it forms about 

 10 per cent. This amount can be increased by feeding, espe- 

 cially if carbohydrates are given in excess. The bulk of man's 

 carbohydrate food is converted into dextrose and levulose, 

 and these when they reach the liver are changed to glycogen 

 and stored. From time to time the glycogen is reconverted 

 to dextrose and given off to the blood, so that the normal sugar 

 content 0.1 to 0.2 per cent, is maintained. The way in which 

 this conversion is brought about is probably through an enzyme, 

 since a diastatic enzyme that changes glycogen to dextrose 

 can be extracted from the liver. Ptyalin converts glycogen to 

 maltose and dextrins. 



Intestinal Glands. It is stated that many cells of the 

 intestinal glands undergo histological changes during activity, 

 in that their granules disappear. Section of intestinal nerves 

 leads to an accumulation of fluid in the intestine; but if the 

 inferior ganglion of the solar plexus is left intact, the accumula- 

 tion does not take place. 



When a portion of the small intestine is separated into three 

 contiguous compartments by ligatures and the nerves passing 

 to the middle compartment are cut, it can be observed that 

 a secretion, a genuine succus entericus, forms in the middle 

 compartment. The secretion may begin in four hours, increase 

 for twelve, and then rapidly diminish so that after two days 

 the compartment is empty like its neighbors. This is looked 

 upon as a paralytic secretion. Mechanical stimulation of 

 the intestinal mucosa gives rise to a local secretion whicfy is 

 an adaptation to the slow movement of the food through the 

 intestine. Such a secretion is poor in enterokinase, but if pan- 

 creatic juice be added, the succus entericus becomes rich in 

 enterokinase. 



Serous Secretions. These are produced by the pleura, 

 peritoneum, tunica vaginalis, and by the synovial membranes 

 of joints, tendon sheaths, etc. The synovial secretion is more 

 glairy and viscid than a truly serous secretion, which is very 

 much like lymph. The function of serous secretion is to prevent 

 friction between surfaces that are in contact. It is of a pale 



