120 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



to the consistency of the pieces, which evidently determined the readiness 

 with which the individuality differential substances were extracted from the 

 tissues. After syngenesiotransplantation, the reactions appeared somewhat 

 later, in accordance with the diminished toxicity of the substances given off 

 by transplants of this type. The reactions to heterogenous grafts consisted 

 in a primary increase in polymorphonuclear leucocytes in the circulating blood, 

 which tended to appear a few days earlier than the reactions to homoiogenous 

 transplants. After heterotransplantation of thyroid tissue, the maximum in 

 the count of polymorphonuclear leucocytes was reached on about the fifth 

 day, approximately two days earlier than the maximum observed after 

 homoiotransplantation ; however, the reaction sets in as early as on the 2nd 

 or 3rd day after the operation, but then a regression in the number of leuco- 

 cytes begins and on about the 10th day a normal count has again been 

 reached. This is followed by a secondary reaction consisting in a relative and 

 absolute increase in lymphocytes, which usually reaches a maximum between 

 the 14th and 16th days and likewise is followed by a regression to normal. These 

 reactions occurred in the guinea pig, rat and mouse with equal regularity. 

 That they were caused by contamination with bacteria can be excluded, since, 

 as a rule, no infection was found, and even where after homoiotransplantation 

 a slight infection with bacteria had taken place, this did not call forth a notice- 

 able increase in the number of polymorphonuclear leucocytes in the blood ; 

 such an increase was observed only in cases in which pus from an abscess, 

 that had formed in and around the graft, had ruptured and escaped into the 

 surrounding tissue. A small number of microorganisms did not therefore 

 cause alterations in the number and distribution of blood cells, such as is 

 seen after transplantation of heterogenous tissues. In these experiments as 

 well as in those in which the local reactions around transplants were studied 

 the results were, on the whole, constant and this fact again could not very 

 well be reconciled with the assumption that bacterial contamination and sub- 

 sequent growth of the bacteria — occurrences which are of an accidental char- 

 acter and therefore necessarily variable — were responsible for these changes. 

 3. A direct attempt was made to follow the fate of bacteria normally ad- 

 hering to pieces of skin after its transplantation, in order to determine their 

 possible role in the attraction of leucocytes. In these experiments, Ermatinger, 

 Queen and Parker transplanted autogenous as well as heterogenous earskin 

 pieces into the subcutaneous tissues; after 1, 2 or 3 days, they were removed 

 for bacterial examination. Autotransplants of skin in guinea pigs, rats and 

 rabbits were studied, as well as heterotransplants from guinea pigs to rats 

 and rabbits, and also the reciprocal transplants. A progressive decrease in the 

 number of bacteria in the skin pieces was found on successive days. The large 

 majority of the microorganisms were destroyed within the first 24 hours, 

 while after 48 hours nearly 25 per cent of the plates were sterile ; after 3 days, 

 sterile plates were found in 62 per cent of the cases and in the rest of the 

 pieces the number of colonies was very small. Staphylococci survived longest. 

 However, during the very hot season a considerable increase in the number 

 of bacteria was observed in the first three days in several instances and the 



