HB. T. Bell 45 
conception of the nature of the corpuscles as Hassall. ‘This oft-quoted 
comparison was therefore not based upon a deep insight into their nature. 
Ginzburg (9), 57, did not advance beyond Hassall’s conception that 
the central mass is formed by the peripheral layers. 
Paulitzky (21), 63, described the center of the corpuscles as homogen- 
eous or granular. They sometimes contain an elliptical nucleus, some- 
times fat droplets. The larger ones have in the center several nuclei’ or 
cell-like forms. The central part is formed from masses of epithelial 
cells. Connective tissue cells grow around them and are transformed into 
epithelial cells forming the peripheral part of the corpuscle. 
The term “ concentric corpuscles ” was introduced by Ecker (6), who 
described them as arising directly from gland cells by fatty meta- 
morphosis. He distinguished (1) simple corpuscles, round vesicles with 
thick concentric hulls, containing inside a fatty opalescent mass, and (2) 
compound corpuscles, which consist of several vesicles with a common 
hull. The peripheral layers of a corpuscle consist of flattened cells. 
His (12 a, 12 b), 60, 80, described the corpuscles as consisting of an 
outer striated shell, probably composed of nucleated cells, and contain- 
ing lymphocyte-like cells inside. He supposed them to be the original 
cells of the epithelial anlage which become entangled in the reticulum in 
some way. Their rapid growth in their narrow confines causes the con- 
centric form. 
Ei 
Cornil et Ranvier (5), 69, considered the corpuscles as arising from 
the endothelium of blood-vessels and compared them to the spheres of their 
“Sarcome angiolithique.” 
This suggestion of a vascular origin, made by Cornil et Ranvier, was 
elaborated by Afanassiew (1a), 77. 
Afanassiew held that the corpuscles of Hassall arise from the endo- 
thelium of the smaller veins and capillaries. The endothelial cells in- 
crease in size, become cubical, and later fill the lumen of the vessel. 
During the proliferation of the endothelium, the blood-vessels break up 
into segments which are now nearly solid cords. These cords are at first 
connected to each other and to blood-vessels, but they soon break apart. 
The surest proof that the corpuscles are of vascular origin is that ery- 
throcytes may be found inside them. Vascular injections, however, do 
not go into a corpuscle except in a very early stage, since the lumen is 
soon obliterated by the endothelial plugs. The corpuscles are formed 
entirely by the endothelial cells. Afanassiew worked on embryos of man, 
the rabbit, and the calf. 
Stieda (26), 81, in sheep embryos, describes the epithelial mass of the 
