NATURE OF CYTOST 241 



magnesium, and phosphorus in all samples examined. 

 Rubidium was present in all the tissues except that 

 of the dog. Traces of boron were found present in 

 the ash of rabbit, rat, dog, and human tissues, traces 

 of lead in the lion tissue, and traces of zinc in the 

 fox tissue, and of aluminum in the cow and horse 

 tissues. 



While these findings were of no especial interest in 

 connection with the cytost problem, the presence of 

 rubidium in all the tissues examined excepting those 

 of the dog is interesting. So far as the writer is aware, 

 no biochemical significance has been attached to this 

 element, although various investigators have from 

 time to time noted that rubidium salts may be substi- 

 tuted for those of potassium in so-called physiologi- 

 cal balanced salt solutions. The traces of heavy metals 

 found in some of the tissues examined are probably 

 attributable to the retention of metals derived from 

 the utensils used in feeding and watering the animals. 



For the present we must conclude that when tissues 

 are ashed at low temperatures in the neighborhood 

 of 300° C, they retain some markedly thermostable 

 organic constituent which is responsible for the physi- 

 ological reactions which follow the injection of solu- 

 tions of the tissue ash into animals. As we have men- 

 tioned before, heating of the tissue ash of all species 

 to 700° in an electric furnace causes the ash to lose 

 its toxic properties. This is exactly what one would 

 expect if the toxic moiety present in the ash were really 

 an organic compound. 



While, as was pointed out at the beginning of the 

 text, we are in complete ignorance as to the exact 

 chemical nature of cytost, the facts stated above testify 



