452 J. A. BADERTSCHER 



sides the normal shaped dark nuclei others are found that are 

 very irregular in outline and greatly distorted. Varying degrees 

 of deformed nuclei can be found between the more deeply stained 

 normally shaped types and the greatly distorted ones. Others 

 are again found that are, without doubt, undergoing degeneration. 

 Figures 2 and 5 represent each a small portion of a section through 

 the thymus head of a 37 and 36 mm. embryo respectively and 

 were drawn specially to show the degenerating cells. ^ In some 

 of the degenerated epithelial nuclei {D.e.N'.) represented in 

 figure 5 the chromatin is massed together in one, two or three 

 clumps that stain intensely deep blue or blue-black. These 

 chromatin masses usually lie in clear spaces around some of 

 which the distorted nuclear membrane apparently still persists. 

 Occasionally a slightly elongated nucleus can be found in one 

 end of which is a clump of chromatin lying in a nuclear vacuole 

 while in the opposite end the nuclear threads and the nucleo- 

 plasm are stained as deeply as that in the nuclei described 

 above. Again, here and there in the cytoplasm of epithelial 

 cells may be found larger and smaller deeply stained parti- 

 cles which are evidently the debris of degenerated epithelial 

 nuclei (fig. 5, D.d.e.N.). To the succession of microscopic 

 pictures — deeply stained and normal shaped nuclei, deeply 

 stained and distorted nuclei, and nuclei that have fallen to 

 pieces — described above and drawn in figures 1, 2, and 5, only 

 one interpretation, it seems to me, can be given, namely, that 

 the deeply stained normal shaped epithelial nuclei are on their 

 way to degeneration and do not transform into lymphocytes. 

 Some of the epithelial cells show signs of degeneration in com- 

 paratively early stages as stated above. They are, however, 

 most numerous and most pronounced in stages from about 

 30 mm. to about 45 mm. in, length. They are also found in later 

 stages and will be referred to again. 



With a proper fixer, a suitable stain, and a high magnification, 

 such as was used for this work, the plump lymphocytes stand 



' Judging from the greater number of lymphocytes present and the great 

 number of completely degenerated epithelial cells, the thymus of the 36 mm. 

 embryo is slightly farther advanced in its development than that of the 37 mm. 

 stage. 



