740 PHYSIOLOGY OF DIGESTION AND SECRETION. 



amount of lymphoid tissue contained in it, and is not a product char- 

 acteristic of the splenic tissue proper. In this connection it may be 

 stated that Jones * has demonstrated the existence in the spleen of an 

 enzyme, adenase, which converts adenin, C 5 H 3 N 4 NH 2 , into hypoxan- 

 thin, C 5 H 3 N 4 OH. The lymphoid tissue of the spleen must also 

 possess the property of producing lymphocytes, since, according to 

 the general view, these corpuscles are formed in lymphoid tissue 

 generally wherever the so-called "germ-centers" occur. (4) Lastly, 

 a theory has been supported by Schiff and Herzen, according to 

 which the spleen produces something (an enzyme) which, when 

 carried in the blood to the pancreas, acts upon the trypsinogen con- 

 tained in this gland, converting it into trypsin. This view has been 

 corroborated by a number of observers, but it is difficult at present 

 to decide whether such an action occurs normally during digestion. 

 As already stated, the general testimony at present indicates that 

 the pancreatic juice when secreted contains its trypsin in inactive 

 form. It is activated only after reaching the duodenum under the 

 influence of the enterokinase. 

 * Jones and Winternitz, " Zeitschrif t, f. physiol. Chemie," 44, 1, 1905. 



