CONCLUSIONS 283 



result of injury are of importance in determining the 

 response of plants to their environment. Most of this 

 evidence gleaned from the vs^ritings of others should 

 be reinvestigated, using extracts of plant tissues in a 

 manner similar to that vs^hich we have employed in 

 our animal experiments. 



If by such methods it can be established definitely 

 that cytost is of equal importance in the plant and 

 animal worlds, we shall have at our disposal a deeper 

 appreciation of an important factor in the physiologi- 

 cal activity of living systems. 



Our experiments have shown cytost to be a substance 

 of remarkable thermostability, but we have failed to 

 identify it as a distinct chemical substance. This is a 

 biochemical problem which still awaits solution. 



So far we have been unable to find any chemical test 

 for the presence of cytost in a tissue extract. The only 

 means of detecting this substance remains the physio- 

 logical reactions described in the text. For laboratory 

 purposes the induction of shock and death in animals, 

 and the localized reaction in the lungs remain the 

 most satisfactory methods for the assay of various cy- 

 tost preparations. While these methods yield positive 

 and unquestionable evidence for the presence of cy- 

 tost, it may be desirable to expand them by the study 

 of the action of cytost on isolated organs. Such a study 

 may give rise to a quantitative method of assay better 

 suited for routine laboratory experiments. 



The development of such methods may be of ex- 

 treme value in future investigations of the action of 

 cytost and its relation to the physiology of the cell, 

 both in health and disease. Certain of our experi- 

 ments have shown that it is possible in young animals 



