250 ILLINOIS ACADEMY OF SCIENCE 



was given off, there being no platinum black on the mesh; 

 hence this piece of mucosa was exposed to the action of the 

 gastric juice in the absence of atomic oxygen. Figure 2B, 

 is a photograph of the piece of mucosa after the preparation 

 had been in the bath for sixty-five minutes. It may be seen 

 that the central circular area exposed to the action of the 

 gastric juice had been completely digested with the formation 

 of a hole. In Figure 2A the oxidation produced by the 

 atomic oxygen liberated at the surface of the mucosa protected 

 it, while in Figure 2B, no such protection being afforded, the 

 exposed circular area was readily digested with the production 

 of what corresponds to gastric ulcer. Figure 2C is a perfor- 

 ating ulcer of the stomach shown for comparison. 



The following experiments were carried out on unicellular 

 organisms to show that when they are introduced into a so- 

 lution of trypsin they protect themselves from being digested 

 by means of their oxidative processes : 



One hundred c.c. of clear pancreatic juice were collected 

 from a cannula in the pancreatic duct of a dog as the result of 

 the repeated injections of secretin into the jugular vein. The 

 trypsinogen in this juice was converted into active trypsin by 

 the addition of 5 c.c. of enterokinase. The resulting trypsin 

 solution was sterilized by exposing it for a few minutes to 

 ultraviolet radiation. It was then placed in a collodion tube 

 and dialyzed against 5 liters of distilled water for twenty- 

 four hours at 10° C. to get rid of most of the dissolved salts. 



Five c.c. of the activated dialyzed juice were introduced into 

 each of two long test tubes. Five drops of water containing 

 a great number of living paramecia were introduced into one 

 tube and another five drops of water containing dead parma- 

 cia, killed by exposure to ultraviolet radiation, into the other. 

 Both tubes were placed in a water bath at 30° C. At the end 

 of three hours, the paramecia, killed by exposure to ultravio- 

 let radiation before being introduced into the pancreatic juice, 

 were completely digested, while those introduced alive were as 

 active as at the beginning of the experiment. At the end of 

 seventy-two hours, when the experiment was discontinued, 

 these paramecia were still alive and very active. 



