54 Transactions of the 



multiplication and development of the nucleated corpuscles of these 

 animals takes place by a process diflTereut from that in the human 

 embryo, we are not justified in supposing that both kinds of blood 

 corpuscles must, necessarily, resemble each other in structure. 

 The details of these researches will form the subject of another 

 treatise. We will now return to the birth-place of the primary 

 human blood corpuscles, and try to prove the identity of those 

 large nuclei, contained within the hexagonal cells, with those 

 mother-blood corpuscles before described. 



The examination of the blood corpuscles, escaping through the 

 cut orifices of the system of canals in the wall of the vesicle, in their 

 fresh and unchanged condition, claimed at first, as mentioned above, 

 the greater part of my attention. The large hexagonal cells I only 

 passingly observed at the margin of the preparation. The larger 

 portion of them, it is trae, were hidden from view by those accumu- 

 lations of blood corpuscles, and, although recognizable by change of 

 focus, no particular attention was paid to their examination at this 

 time. It was, therefore, not until the following day, the prepara- 

 tion having in the meantime been subjected to the action of the 

 solution of chromic acid, and a considerable portion of the blood 

 corpuscles having escaped from the follicles, as well as from the 

 canals, that I recognized the true nature of these cells. As far as 

 I could remember from the previous examination of the fresh speci- 

 men, the large nuclei, contained within the latter, were not coloured 

 and showed a double contour. But, as the greater portion of them 

 were obscm-ed by the blood corpuscles, it is not impossible that they 

 existed here in different stages of development, and that a number 

 of them were already more or less provided with the characteristic 

 colouring matter of the blood. Had this really been the case, they 

 would, nevertheless, subsequently, hke the large mother-blood cor- 

 puscles, have become discoloured by the chromic acid solution, and, 

 consequently, have appeared with a double contour. 



To convince myself more fully of the correctness of my view, I 

 examined the wall of the umbiUcal vesicle, situated between the 

 amnion and chorion of a human embryo, 16 mm. in length. The 

 embryo was one of the best specimens on which I had worked, as 

 it came into my possession only a few hours after its abortion, in a 

 very fresh and, as it appeared, in every respect normal condition ; 

 and although it had at the time of this examination remained several 

 months in a weak solution of chromic acid, still it nevertheless 

 showed sufiiciently the structure of its umbilical vesicle. The wall 

 of the latter proved to be a membrane consisting of a delicate fibrous 

 tissue, the interior surface of which served as a base to a tolerably 

 thick layer of those large hexagonal cells. These appeared some- 

 what shrivelled, granular and of a greenish yellow tint, but although 

 still hexagonal in foim, they had nevertheless lost the well-defined 



