The Microscope. ;^73 



was collated, the result showing that as the pigment of the "Ammen- 

 zellen " decreased, the number of the circulating red corpuscles 

 became greater, the quantity of undeveloped corpuscles inci'eased, 

 and that many of the circulating corpuscles were still bordered with 

 granules of pigment. Another indication that blood-building ele- 

 ments are present in the " Ammenzellen " was the iron reaction which 

 the protoplasma gave with potassium ferrocyanide. From these 

 observations it seems hardly to be doubted that red blood-corpuscles 

 are developed in the "Ammenzellen," and partially at least in the 

 endothelial cells, and in the " endotheloid cells." The relation in 

 which these three cells stand to the blood-vessels remains to be con- 

 sidered. The blood-vessels of the embryo have their origin, as the 

 embryologists have taught us, in the mesoderm in chains of endoth- 

 elial cells which contain clear spaces in their protoplasma that later 

 <;omtuunicate with one another to form a fine capillary, in whose 

 walls the first red blood-corpuscles are formed. Keturning to the 

 . spleen, we recall the fact that the " Ammenzellen " groups lie 

 between the capillaries of the arteries, with their endothelial cells on 

 the one hand and the capillaries of the veins on the other hand, and 

 that between the in-llowing and out-flowing vessels the regular blood- 

 vessels with their lining ceils fail. It is, then, not difiicult to sup- 

 pose that the " Ammenzellen " and the " endotheloid cells," which 

 are so numerous in the spleen, might be the stage upon which, as in 

 the mesoderm of the embryo, a constant building of new blood- 

 vessels and blood- corpuscles is taking place. The white blood-cor- 

 puscles of the frog may perhaps be looked upon as undeveloped 

 " Ammenzellen," though their origin and the functions peculiar to 

 each form are not yet clear. It is significant that a seeming rela- 

 tion exists between the coagulation of the blood and the formation 

 of white blood-corpuscles, for as the blood of the frog begins to 

 coagulate the " hsematoblasts " become especially numerous, and 

 group themselves characteristically; but to this point we shall refer 

 again in connection with human blood, which is in many points sim- 

 ilar to the blood of the frog. 



The red blood -corpuscles of human blood contain, as is known, 

 no nuclei. In our preparation they retain the disk form and color, 

 like the protoplasma of the red corpuscles of the frog with eosin. 

 The white blood- corpuscles are represented by the two forms 

 '' eosiuophilous cells " and amoebocytes." The " hsematoblasts," as 

 such, are wanting in human blood, but since we have had our atten- 

 tion directed by Hayem to the fact that the *■' hgematoblasts " play an 

 important part in the coagulation of the frog's blood, it is possible 



