The injection of rabbits' placenta into rabbits produces no isoprecipitins.

From the incomplete experiments performed it would appear that placental injections into animals of the same species cause no changes in the generative organs. Further research into this question will be pursued.

The injection of human placental nucleo-proteid, prepared from placental tissue made nearly blood free, does not produce an antiserum. This result confirms the conclusions of Pearce and Jackson, that nucleo-proteids act merely as mild toxic agents, without specific qualities.

The injection, into rabbits, of human placental tissue, rendered practically blood-free, fails to produce any specific reaction. This confirms the view that the serum reaction following the injection of cells into a foreign organism is largely due to the blood contained in the injected tissues.

The injection into rabbits, of the human placenta, made nearly blood-free, produces a weak " human reaction " which can be demonstrated by the reactions for precipitin, deflection of complement, agglutinin, and hemolysis. No specific placental reaction can be shown. This is in strict accord with the view that cytotoxines are not specific; that there is no morphological specificity.

The anti-sera obtained showed no cytolytic action; therefore no specific syncytiolytic action could be demonstrated.

If the information obtained in this investigation is applied to the theory of Halban, it will be noted that no experimental proof of the specific action of placental tissue upon the female generative organs could be demonstrated. The number of experiments performed, bearing upon this one point, were however too few to permit of a definite and final opinion.

The work dealing with Veit's ingenious hypothesis was more complete and carried out by many methods, which would necessarily act as a check upon one another. As the results of all these experiments were in complete harmony, I feel justified in making a positive statement that no experimental proof of a specific placental immune reaction can be demonstrated by our present biological methods. Whether Veit's hypothesis, thus deprived of its biological proof, must in consequence be discarded, is a question which I do not consider myself competent to answer.

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