46 The Development of the Thymus 
thymic anlage as being broken up by ingrowing adenoid tissue. From 
50 mm. to 60 mm., there are no large epithelial cells; but later at 100 mm. 
he finds in the adenoid tissue large cells 9 w to 15 » in diameter, isolated 
or united in groups, whose protoplasm colors light-red with carmine. 
These large cells have a concentric structure. Some of them are enclosed 
by large cells whose cytoplasm does not color with carmine, giving rise to 
a yellowish mass of irregular form and stratified appearance. In older 
embryos (250 mm.), the cellular masses are numerous but the large 
colored cells are rare. ‘The yellowish masses are groups of the large cells 
which have undergone a transformation like that of the stratum corneum 
of the epidermis. Stieda considers the large colored cells which form 
the corpuscles as remnants of the epithelial anlage, although he admits 
that for a long period during development he found no trace of them. 
He explains the formation of the corpuscles in accordance with Cohn- 
heim’s hypothesis that most tumors arise from unused tissue remnants. 
Ammann (2) 82, made most of his observations on human fcetuses. 
He describes the corpuscles as arising from connective tissue. ‘The cor- 
puscles are cellular in structure and are formed of one, two, or three cen- 
tral cells around which a variable number of cells, increasing with age, 
are arranged like the coats of an onion. The corpuscles are formed from 
reticulum cells and leucocytes. Growth consists in the apposition of cells 
from without. The life of a corpuscle consists usually of four stages: 
(1) Stadium der Transparenz; (2) Stadium der colloiden Entartung ; 
(3) Stadium der Verkalkung; (4) Stadium des Zerfalls. The nucleus 
of a reticulum cell or leucocyte increases in size at the expense of the 
cell body. Its increase in size establishes the concentric form. The 
corpuscle undergoes colloid and usually calcareous degeneration. Fat 
droplets, cholesterin crystals, and colloid granules are found together in 
the degenerating corpuscles. Breaking up in this way makes absorption 
possible. No epithelial remnants are to be observed. No erythrocytes 
are found in the corpuscles. 
In four cases of atrophic thymus gland which yet contained lymphoid 
tissue Ammann found corpuscles in all stages of development. He also 
found that the corpuscles are formed most rapidly when the thymus is 
at the height of its development. From these facts he concluded that 
they are not connected with the involution of the thymus as Afanassiew 
thought. He thought that their formation is due to a physiological de- 
crease in the intensity of growth of the medulla, due to the rapid growth 
of the cortex. : 
Watney (31), 83, agreed with Ammann that the corpuscles arise from 
connective tissue cells. 
