1913] Sweet: Epithelioma of the Common Fowl 39 



Nature of Inclusion. — It seems that epithelioma eontagiosum 

 produces a very rapid proliferation of epithelial cells, those cells 

 which are in a state of proliferation remaining free from visible 

 cell inclusions. This would suggest that this cell inclusion, in 

 its enlarged state at least, appears in a cell only after its birth 

 as an independent cell, and that it is only after the cell is no 

 longer proliferating that the cell inclusion appears. This would 

 at once lead one to label the inclusion as a product of cell 

 degeneration, as Burnet (1906), Apolant (1902), Marx and 

 Sticker (1902) have done for this disease, and as Ewing (1904) 

 has done for the inclusions seen in vaccina. However, the fact 

 that in the neighborhod of the proliferating zone many cells 

 appear which contain well marked cell inclusions, but which show 

 little or no evidence of degeneration, makes one hesitate to make 

 so absolute a conclusion. So if one assumes that the cell inclusion 

 is merely a product of cell degeneration he must assume that it is 

 due to some chemical change within the cell which does not 

 manifest itself as a usual type of degeneration until late in the 

 life of the cell. This does not seem a very difficult assumption 

 to make in view of the very extensive changes produced in the 

 epithelial elements. 



Changes in Inclusions. — As mentioned above, in passing from 

 the proliferating zone inward to the center of the epithelial cell 

 ne-sts, progres-sive degeneration of the cytoplasm and nucleus are 

 seen. Apparentlj^, the same progressive degeneration is seen in 

 the cell inclusions. In the region of the proliferating zone the 

 cell inclusions stain deeply, and are clear cut in outline, but as 

 one goes away from this zone toward the center of the epithelial 

 bud they stain less deeply, have less clearly defined margins, be- 

 come increasingly vacuolated and finally are completely disin- 

 tegrated. Here again one is tempted to ascribe all this change 

 to progressive degeneration, but is deterred by remembering that 

 it so very closely follows the normal sequence in the life cycle 

 of protozoan cell parasites. Very often there appear smaller 

 bodies within the cell inclusions, giving them something of a mul- 

 berry appearance. This occurs often enough and is so well 

 marked that it very strongly suggests the presence of a stage 

 of sporulation. Also in fixed preparations stained with Giemsa 



