BLOOD: ITS GENERAL PROPERTIES 91 



the removal of the antitrypsin and the action of the protease normally 

 present in the blood. 



Nuclein ferments are capable of decomposing nucleic acid and purins 

 into the simpler bodies. 



Lipases have been demonstrated in the blood. 



Amylase. The presence of starch-splitting ferments in the blood was 

 first shown by Magendie in 1841, and later Bernard showed that gly- 

 cogen or starch injected into a vein produced glycosuria. Since then 

 it has been proved conclusively that diastatic enzymes are normally 

 present in the blood and lymph. The source of these enzymes has given 

 rise to much speculation. Some observers believe that they are derived 

 from the amylopsin of the pancreatic secretion, while others believe that 

 they are manufactured by the liver. Ligature of the pancreatic ducts 

 is said to increase the amount of amylase, while removal of the pan- 

 creas may (Carlson and Luckhardt) or may not (Schlesinger) increase 

 the amylase of the blood. In some forms of experimental diabetes the 

 amylase of the blood has been found increased, and this is the case in 

 human diabetes (Myers and Killian). If this is true, a cause for the 

 inability of the diabetic to store up glycogen is found. In impairment 

 of renal function, there is usually an increase in the blood amylase and 

 a decrease in the urine amylase. This has been suggested as being of 

 diagnostic value. 



The blood contains a feeble glycolytic enzyme capable of destroying 

 glucose. It is claimed that this power is reduced in diabetics (Lepine). 



Catalase is found in the blood and tissues generally. It has the power 

 of liberating oxygen from hydrogen peroxide without any accompany- 

 ing oxidation process. Its physiological significance is not known. It 

 is said that the amount of catalase is increased during excitement and 

 exercise, and is decreased in conditions where the body's activity is 

 lowered. Its determination is clinically unimportant at present. 



