CONCLUSIONS 281 



the quantity of cytost liberated may greatly exceed 

 the quantity sufficient for healthy stimulation of the 

 tissues, and a mild toxic action may become apparent 

 some hours afterwards. In some degree the severity 

 of such a toxemia is found roughly to parallel the ex- 

 tent of the tissue injury caused by the sunlight. Of 

 course individuals vary in this respect. Some active 

 persons can contract a markedly destructive and pain- 

 ful sunburn v^ithout any apparent general ill effects. 

 Presumably such individuals, through previous activi- 

 ties, have developed a resistance to cytost comparable 

 to that v^hich follov^s a series of immunizing injec- 

 tions. 



The essential point to be gleaned from the fore- 

 going is that cytost occupies a unique role in the 

 activity of cells, for through its action such activity 

 is closely determined by alterations in the environ- 

 ment. Of course the response of cells to all conceiv- 

 able environmental modifications cannot be dependent 

 solely upon the action of cytost, but the evidence v^hich 

 the w^riter has accumulated points strongly to the fact 

 that many changes in cellular activity are uniquely 

 controlled by the liberation of cytost under the influ- 

 ence of environmental factors. This is a point not 

 generally appreciated by v^^orkers in the biological 

 sciences at the present time, and the w^riter is con- 

 vinced that the adoption of this viev^ may do much 

 to effect a rational explanation of many apparently 

 uncorrected biological facts. 



It is the v^riter's earnest hope that other investiga- 

 tors w^ill attempt to repeat and extend his observations. 

 Certain of our researches, although prosecuted to the 

 fullest extent w^hich available facilities permitted, still 



