400 INTERNAL SECRETIONS OF PANCREAS AND SPLEEN. 



as clear evidence that overactivity of the pancreas could also 

 be ascribed to these organs. Again, the ease with which oxy- 

 gen is thought to convert trypsinogen into trypsin a mere 

 current of oxygen through a solution of zymogen sufficing to 

 produce trypsin has been fully emphasized. Besides Heiden- 

 hain's labors in this connection, we need but recall SchifFs ex- 

 periment with the two halves of a pancreas, one of which was 

 infused at once and the other left exposed to the air a day, 

 with the result that the latter alone proved active; and also 

 that of Herzen, in which an infusion of active spleen mixed 

 with an infusion of inactive (hence zymogen-laden) pancreas 

 proved very active, while a pancreatic infusion mixed with one 

 of inactive spleen digested nothing. Heidenhain ascribed to 

 oxidation the conversion into trypsin, in this experiment. In- 

 deed, when we consider the wealth of oxygen in the blood 

 supplied the pancreas, direct from the lungs via the cceliac 

 axis, it would seem as if it should be the predominating factor 

 of the conversion processes involved. 



And yet, the oxidizing substance being a constituent of 

 the blood-plasma, it would have to penetrate into the ducts 

 per se and as oxidizing substance in order to carry out the 

 required reaction. There is no evidence that a direct chan- 

 nel, such as there is in the spleen, by means of which the 

 capillaries directly pour their blood into the secreting struct- 

 ures, exists. As may be seen in the annexed illustration, the 

 splenic vessels actually terminate in the latter; "their walls 

 become much attenuated, lose their tubular character, and the 

 cells of the lymphoid tissue of which they are composed be- 

 come altered, presenting a branched appearance and acquiring 

 processes which are directly connected with the processes of 

 the sustentacular cells of the pulp." 24 



Nor is there evidence that canaliculi such as those of the 

 hepatic cell exist by means of which the blood-plasma or its 

 contents may directly find their way to a structure correspond- 

 ing to bile-channels, which in the pancreas would be repre- 

 sented by the ducts. Langerhans long ago demonstrated that 

 canaliculi were present in the lobules between the epithelial 



24 Pickering Pick and Howden: "Gray's Anatomy," 1901. 



