BIOLOGICAL DIAGNOSIS OF PREGNANCY 95 



continuance leads to the appearance of insufficiently 

 decomposed products. Involution, too, may be the 

 cause of the formation of products that are out of 

 harmony with the blood ; in which connection we have 

 in mind more especially the degeneration of the 

 thvmus, and the climacterium. 



J 



Many of our own researches, and those of various 

 j 



observers, have shown that, during the whole period 

 of pregnancy, defensive ferments circulate in the 

 blood, which are able to reduce placenta albumen. 

 These ferments may be demonstrated within about 

 eight days after impregnation. Their presence is, 

 without any doubt, dependent upon the circulation 

 of disharmonious substances originating in the 

 placenta ; since the defensive ferments disappear 

 within fourteen to twenty-one days, when the 

 relations of the placenta with the maternal organism 

 have ceased. 



Attempts have also been made to decompose 

 placental tissues by means of the blood serum of the 

 foetus. No digestion could be induced; nor can the 

 serum of pregnant individuals be made to attack 

 the tissues of the foetus. In any case these obser- 

 vations must be carefully followed up. It might 

 be imagined, a priori, that there are develop- 

 mental stages, in which the tissues of the foetus are 

 as yet so little differentiated, that they are still of a 

 generalized character. Xor did umbilical blood 



