THE LYSim. 139 



of the mother. On the other hand, fetal blood is richer in inorganic 

 salts, especially the insoluble salts, than is the blood of adults. 

 Furthermore, fetal blood is richer in sodium, poorer in potassium, 

 and the total quantity of chlorin not combined with either potassium 

 or sodium is markedly smaller than in the blood of adults. 



B. It also follows from these experiments that the maternal blood 

 often contains agglutinins while the fetal blood shows no trace of 

 these substances ; and inasmuch as the fetus must obtain albuminous 

 substances from the maternal blood in the construction of its own 

 tissue, and as the agglutinins are supposed to belong to the globulins, 

 it follows that all albuminous substances are not absorbed by the 

 fetus from the mother equally and that there must be a selective 

 absorption manifested by the epithelium of the chorion. 



O. This investigation bears upon the question of the origin ot 

 normal agglutinins in the blood; of course, it has nothing to do 

 with specific agglutinins produced by inoculation. Since agglutinins 

 are present in the blood of the mother, it has been supposed that 

 those found in the blood of the fetus have simply been transferred 

 from the former to the latter, but the above-mentioned experiments 

 contradict this view, inasmuch as it was shown in some instances 

 that there are agglutinins in fetal blood while they are not present 

 in the blood of the mother. We must, therefore, suppose that these 

 substances originate independently of the mother, and we should 

 distinguish between inborn and hereditary agglutinins and lysins. 

 Ehrlich and Morgenroth have proved the existence of isoagglutinins 

 and isolysins, but it is claimed by Halban that these must be sub- 

 divided into ordinary isoagglutinins and isolysins on one hand, and 

 idio-isoagglutinins and idio-isolysins on the other, meaning by the 

 last given terms his inborn, non-hereditary substances. To account 

 for the origin of these idio-iso-substances, Halban offers the follow- 

 ing theories : (1) The idio-iso-agglutinins and idio-isolysins are due 

 to an interchangeable immunization between mother and fetus. 

 Blood cells in both circulatory systems are constantly disintegrating 

 and the products of their disintegration may pass from mother into 

 fetus and vice versa, and by this means an interchangeable immuni- 

 zation may be produced. The fact that the agglutinins are more 

 frequent in the blood of the mother than in that of the fetus may 

 be explained on the supposition that the fetus does not form agglu- 

 tinins so readily. Halban supposes that this theory has some sup- 

 port in the demonstrated fact that children infected with typhoid 

 fever during the first year of life as a rule show the Widal reaction 

 less promptly than adults do ; and he states that it has been shown 

 by Schreiber that newly born infants bear without apparent effect 

 doses of tuberculin which induce in adults marked elevation of tem- 

 perature. Halban admits that the presence of agglutinins in the 

 blood of women who have never borne children, and also in the 



