60 Transactions of the 



in form. It is not impossible that amoeboid movements had already 

 taken place in the latter before the death of the embryo set in. A 

 large number of coloured blood corpuscles had assumed a cup-shaped 

 form. Although a number of young coloured corpuscles, either 

 free or still attached to the mother-corpuscle, were observed here 

 too, they were, however, not so numerous as in the pulp of the 

 spleen. 



In the blood of the foetus of 5^ months, the endogenous process 

 of formation has, finally, almost entirely ceased. The number of 

 mother-corpuscles containing embryo-corpuscles, is here quite small. 

 Nevertheless a number of them, discoloured and double -contoured 

 by the action of chromic acid, and marked by concave depressions 

 and slits, from which the embryo-corpuscles had escaped (Fig. 9, h), 

 I still found in the right auricle of the heart. Besides these I also 

 found there a number of coloured blood corpuscles not fully de- 

 veloped, which, although still surrounded by a colourless membrane- 

 like envelope thrown into irregular folds, betrayed their true cha- 

 racter by their colour (Fig. 9, a). In the most of these cases the 

 envelope embraced only one of these bodies, but in some three or 

 four. In the spleen I met with the same bodies, only in smaller 

 numbers ; in one case I observed a blood crystal in the centre of 

 the coloured body (Fig. 9, a). It is very probable that these bodies 

 represented colourless blood corpuscles, the nuclei of which were in 

 their last stage of metamorphosis into coloured blood corpuscles. 

 This view is corroborated by the circumstance that a number of 

 colourless blood corpuscles were observed in company with them. 

 The shrivelled appearance of the envelope was probably due to the 

 action of chromic acid, in a solution of which the foetus had been 

 lying for several days with the thorax opened. 



From the foregoing examinations, it can be seen that with the 

 appearance and the steady increase of the colourless blood cor- 

 puscles in the blood of the human embryo, the endogenous formation 

 of the coloured corpuscles gradually decreases. But as I did not 

 extend these examinations beyond the last-mentioned period, I am 

 not able to state exactly the time when this formative process ends ; 

 very probably at birth, when the embryo has arrived at full matu- 

 rity, and begins its independent existence with its first inspiration. 

 Notwithstanding, small coloured mother-blood corpuscles, containing 

 a small embryo-corpuscle, are still met with now and then in the 

 blood of the adult ; their diameters, however, never exceed that of 

 the matured corpuscle. 



If we accept now the generation of the primary coloured blood 

 corpuscles in the human embryo in its earliest stages of development, 

 as taking place in certain glandular cells destined for this purpose, 

 the question next arises, what is the first momentum which sets them 

 in motion ? According to those existing theories, already partially 



