NATURE OF THE INDIVIDUALITY DIFFERENTIALS 197 



entials was glycerine or a 0.9% solution of sodium chloride, saturated with 

 thymol. In the latter, the individuality differentials were active in the majority 

 of cases after immersion for 24 hours, and in the former, after immersion for 

 12 hours. In acetone and in half molar sodium benzoate, the transplants in 

 most cases were inactive after immersion for one hour, but some remained 

 active; after 12 or 24 hours immersion, they all had become inactive. In 95% 

 alcohol, 37% formaldehyde, and one-half saturated solution of ammonium 

 sulfate, all the pieces were inactive after immersion for one hour. Treated 

 with 50% urea, less than one-half of the pieces were active after immersion 

 for one hour; with one-half molar ferrous chloride and with 1/200 molar 

 ferrous chloride for six hours, all the pieces had become inactive. 



The substances used in these experiments may act in either of two ways : 

 (1) some may extract the homoiogenous differentials, and (2) others, espe- 

 cially those which affect the proteins, probably injure or destroy the homoiog- 

 enous differentials. Among the latter, most effective are those substances 

 which actively denature protein. In general, the homoiogenous differentials 

 proved to be very sensitive to chemical substances of various kinds and par- 

 ticularly to substances which alter proteins. There is reason for assuming that 

 these differentials are produced only in living tissues, inasmuch as the ma- 

 jority of the pieces of tissues which had become ineffective, after having been 

 subjected to the action of such a chemical, had been killed or severely injured. 

 If, under these conditions, merely a newformation of the individuality 

 differentials had been prevented, it should have been possible at least for the 

 differentials preformed in the tissues to be potent. However, as stated, it 

 seems that the majority of the chemicals used injured also these individuality 

 differential substances as such. 



It is of interest to compare with these reactions, those in which Blumen- 

 thal introduced various proteins, carbohydrates, fats, or lipoids subcutaneous- 

 ly. Substances which were liquid were injected subcutaneously on successive 

 days. The proteins caused a reaction in the peripheral blood, similar to that 

 induced by homoiogenous differentials. But it differed from the latter reaction 

 in that the response of blood cells was not destroyed by a preliminary ex- 

 posure of these protein substances to heat. Heterogenous rabbit serum and 

 heterogenous embryonic tissue behaved like these protein substances ; they 

 elicited merely an increase of lymphocytes in the blood, which appeared 

 between the second and fourth day after implantation of the foreign protein. 

 None of the non-protein substances gave rise to this reaction. 



From these experiments, it follows that as far as the effects of strange sub- 

 stances on the white blood cells circulating in the blood vessels indicate there 

 is a definite order in which these substances can be arranged. (1) The finest 

 gradations in the reactions are found if substances possessing strange indi- 

 viduality or species differentials are introduced. The reactions here correspond 

 to the genetic reationship between host and donor. (2) Next come substances 

 of a protein nature, which cause reactions not unlike those produced by 

 homoiogenous differentials ; the former elicit more marked reactions than those 

 brought about by autogenous individuality differentials, which themselves 



