PHYSIOLOGICAL AND BIOLOGICAL RELATIONS 95 



Dzierzgowski and Sieber-Schoumoff (101) in 1901 indicated a great re- 

 sistance of abrin to the digestive enzymes. Hausmann (i 51) in 1902 

 found that the toxic and agglutinating properties of abrin were not 

 impaired by trypsin digestion. Sieber and Schumoff-Simonowski (5 1 5) 

 showed that neither erepsin nor intestinal juice destroyed the toxicity 

 of abrin, nor did digestion with trypsin followed by that with intestinal 

 juice. The slight weakening of the toxicity which they observed they 

 attributed to the long exposure to the relatively high temperature em- 

 ployed in the digestion. Rochat (432) stated that the agglutinating 

 power of ricin was destroyed by digesting with gastric juice prepared 

 according to Pekelharing's method and that trypsin did not have so 

 strong an action on the ricin. Osborne, Mendel and Harris (365) 

 found that the agglutinating power of their preparations of ricin was 

 destroyed or diminished by prolonged digestion with trypsin and that 

 the toxicity was also either destroyed or greatly diminished. 



The evidence thus recorded apparently strongly favours the view 

 that these toxalbumins are not destroyed by proteolytic enzymes, but 

 an examination of the details of the experiments which have been 

 tried leaves one much in doubt as to the weight which should be 

 attached to them. The earlier experiments with ricin were all made 

 with crude preparations which have since been shown to contain but 

 little toxine, and were made at a time when the enormous toxicity of 

 this substance was not appreciated. It is therefore almost certain that 

 the relatively short periods of digestion employed in most of these ex- 

 periments would leave much ricin unattacked. The same is true of 

 experiments with abrin. 



It is evident from all the experiments which have been made that 

 ricin is not easily altered by proteolytic enzymes. Assuming, however, 

 that it is not thus altered it would even then be questionable whether 

 or not this could be considered as good evidence of its non-protein 

 nature, for proteolytic enzymes act very differently on different forms 

 of protein. Thus erepsin easily hydrolyses the primary proteoses and 

 casein, but has no action on other native proteins. Trypsin digests 

 many of the proteoses with the formation of free amino-acids, but a 

 part of the polypeptide-like products which result from its action on 

 the native protein resists its further action. It also readily digests 

 many of the synthetic polypeptides, but is without action upon others. 

 That there should exist in nature a form of protein which cannot be 

 hydrolysed by proteolytic enzymes would not be surprising, and the 

 fact that these toxalbumins produce such remarkable and powerful 

 physiological effects upon animals would indicate that they differ in 



