The origin and histogenesis of the thymus in Raja batis. 455 



Cavy No. 1 (42 days). The picrocarmine preparations are only 

 of interest as throwing more light upon the chromatolytic phenomena. 

 In the haematoxylin-preparations in section the concentric corpuscles 

 are seen to measure 0.04—0.06 in diameter. There is no great change 

 from the conditions witnessed in the preceding specimen, but the 

 cells of the concentric corpuscles are more chromatolytic. The epi- 

 thelial strands are not obvious in all the lobes, but they appear to 

 be extending. 



Cavy No. 3 (f>5 days). Again, the picrocarmine preparations only 

 bring into prominence the chromatolytic phenomena. The concentric 

 corpuscles now stain a bright red with eosin, and they are quite 

 visible to the naked eye. Their distribution is more extensive, and 

 they are met with, apparently, in every lobe. Attached to them in 

 network-fashion are long epithelial branches. The columns of con- 

 centric corpuscles are no longer simple, but multiple, three or four of 

 the branches being often together in one section. They now present 

 a very obvious concentric arrangement of cornified and degenerate 

 epithelial cells. Often there are heaps of leucocytes in degeneration 

 included in the concentric capsule. In other sections there are none 

 of these. The component cells of the corpuscle are absolutely degener- 

 ated, and exhibit very marked chromatolysis. In many sections the 

 interior of the corpuscle is stained a bright red, the rest is purple, 

 and the cortical portion especially shows a laminated arrangement of 

 the remains of epithelial cells. Often there is vacuolation present. 

 In these also degenerated leucocytes and debris of such are in evi- 

 dence. Chromatolysis is now seen in the epithelial strands above 

 referred to. In section the corpuscles measure 0.12—0.14 mm. 



New-born cavy. There is no great increase in size in the earlier 

 formed corpuscles, but numerous smaller ones are noted. The corni- 

 fication and vacuolation are marked. The large ones contain degenerate 

 leucocytes and the debris of such. Chromatolysis is less marked, be- 

 cause this is practically over. Epithelial strands are still present in 

 various places. 



Examination of the concentric corpuscles of cavies of similar ages 

 to the last two dealt with will reveal the great differences between 

 these bodies here and in such an animal as the cat, for instance. Of 

 them, as seen in the older specimens, I have given no figures, for 

 they are so complex and so brilliantly coloured, that only an artist 

 could do justice to them. 



The foregoing observations upon the concentric corpuscles of the 



