NATURE OF CYTOST 239 



the heterologous ashes could cause death, provided 

 the dosage was sufficiently high. The relative species 

 specificity became strikingly apparent only when we 

 compared the minimal lethal doses of the heterolo- 

 gous ashes with that of the homologous ash. 



It follows from this that the apparent species spe- 

 cificity which we have observed in our experiments 

 is due not to a particular component of the ash unique 

 to a given species, but rather to the quantitative dis- 

 tribution of a component common to the ash of several 

 species. Thus if it be assumed that a certain concen- 

 tration of this component per unit weight of ash is 

 necessary to elicit in the cat the various symptoms 

 which follow injection, it may be imagined that the 

 concentration of this component in the ash of rat tis- 

 sues is comparable to that which exists in the ash of 

 cat tissue, in consequence of which solutions of the 

 same strength of these two ashes will be about equally 

 toxic when administered to cats by any of the routes 

 we have mentioned above. Conversely, we may as- 

 sume the ash of other heterologous tissues which we 

 have used in our experiments to contain less of the 

 active component than cat or rat tissues; hence when 

 injected into cats a larger dosage of such ashes will 

 be necessary to evoke reactions comparable to those 

 obtained with cat and rat tissues. 



This concept is purely speculative, but is sugges- 

 tive of further experiments. Thus, if it is true, one 

 should be able to ascertain a quantitative relation- 

 ship between the toxicity of a series of heterologous 

 ashes for animals of different species. 



As yet we have no inkling as to the nature of the 

 toxic component present in tissue ash. One is strongly 



