Bode bas tae AY 
Monguidi (18), 85, distinguished true and false concentric corpuscles— 
the latter being only sections of blood-vessels. 
Hermann et Tourneux (11), 87, gave a description of the structure 
and formation of the concentric corpuscles about like that given by 
Ammann except that they regard the reticulum cells from which the 
corpuscles develop as of epithelial origin. 
Gulland (8), g1, regarded the corpuscles as epithelial remnants and 
compared them to the epithelial pearls of the tonsil. 
Maurer (17 c), gg, described the corpuscles as epithelial in origin. 
His description of their formation is however different from that of His. 
All the cells of the epithelial anlage at first assume a lymphoid character. 
Later, some of these cells reassume their epithelial nature and then form 
the corpuscles. His conclusions for teleosts and amphibians are similar 
to the above results which he obtained from the lizard. 
Ver Eecke (28), 99, for the frog, describes the leucocytes and con- 
nective tissue cells as invading the thymic anlage and separating the epi- 
thelial cells. The epithelial cells, separated by the mesenchymal elements, 
lie at first in groups or singly. They go through a cycle of two phases, 
a stage of growth, and a stage of involution. In the former stage, they 
increase to three or four times their original size and their cytoplasm 
differentiates into circular layers like the coats of an onion. The majority 
are monocellular. Some cells grow together making a more complex 
multicellular type. There are some intermediate forms, cells with a dense 
dark protoplasmic body, indistinct striations, and a nucleus partly or 
completely hidden in a precocious degeneration. In the stage of in- 
volution, which sets in early, the cytoplasm degenerates by the formation 
of vacuoles containing a hyaline liquid. The liquefaction may be in the 
form of a diffuse vacuolization, a large central vacuole, or a peripheral 
vacuole circular in section. The nucleus loses its affinity for stains, be- 
comes deformed, breaks up, and finally disappears. The corpuscles are 
finally absorbed. They never contain erythrocytes. The cells do not de- 
generate to form a corpuscle. The liquefaction forms an internal secre- 
tion which is forced out by the muscle tissue in the reticulum. 
Entirely different results on amphibians are reported by Nusbaum and 
Machowski (19), 02. These investigators revive the old idea of Afan- 
assiew, accepting his results except that they think the adventitia as well 
as the endothelium of the blood-vessels takes part in the formation of the 
corpuscles. They find erythrocytes in the corpuscles. These erythrocytes 
either gradually shrivel and disappear, or they are absorbed by leucocytes 
or endothelial cells. The leucocytes after digesting the hemoglobin of the 
erythrocytes become eosinophile cells which are numerous in the thymus. 
