372 The Microscope. 



assume the forms mentioned above, the nucleus and cell as a whole 

 become I'ound, and at length send out pseudopodia in every direc- 

 tion, so that it is impossible to distinguish them from " amcebocytes.'^ 

 The " amcebocytes," in their turn, at first stretch out their pseudopo- 

 dia in a lively manner, then gradually attach themselves to the cover- 

 slip, where they spread themselves over a large surface, and resem- 

 ble the " endotheloid cells " with their broad borders of hyaline sub- 

 stance and the granulated protoplasma about the nucleus. If we 

 now bring together the facts we have observed, — 1, in instantly fixed 

 blood; 2, in blood fixed after intervals; 3, in fresh blood, — we find 

 that the first three kinds of white blood-corpuscles may at length 

 become "endotheloid cells." 



AVhat is, then, the fate of the "endotheloid cells?" Are the 

 bodies we have described as lying in their protoplasma and resem- 

 bling incomplete blood-corpuscles to be considered as such ? The 

 endothelial cells which they resemble are, as is known, broad, flat 

 cells, that lie spread out on the inner surface of the blood-vessels 

 similarly as the " endotheloid cells " flatten themselves out on the 

 cover-slip. Their protoplasma is colored with nigrosin, and in the 

 small capillaries, where one or two cells sufiice to form the circum- 

 ference of the capillary, has been observed to contain pigment and 

 more or less developed red blood -corpuscles. Especially is this the 

 case in the liver and spleen of the fi'og. If the spleen be teased out, 

 and its cells fixed and colored in the manner mentioned above, not 

 only do we find that the number of white blood-corpuscles, especially 

 of the " endotheloid cells," is much larger in proportion to the red 

 blood-corpuscles than it is in circulating blood, but other cells are 

 present which possess the general characteristics of " endotheloid 

 cells " and endothelial cells. They are richer in pigment, contain 

 often several undeveloped red corpuscles, and cling together in 

 groups. Gaule, in his Strassburg lecture, called these cells "Ammen- 

 zellen," because in them he observed the development of the red 

 blood-corpuscles. In the course of his observations of a series of 

 frogs he noticed that the " Ammenzellen " which lie in groups simi- 

 lar to the follicles of the animal spleen, between the arteries enter- 

 ing and the veins leaving the spleen on the periphery, undergo sig- 

 nificant changes, normally, in the course of the winter, under the 

 influence of pilocarpine, in a few hours. The result in both cases 

 was the same. The "Ammenzellen," at first rich in pigment, lose 

 their pigment as the number of undeveloped corpuscles increases. 

 At the same time the number of corpuscles in the circulating blood 



