EPITHELIAL CAECINOMATA. 205 



with a large number of parallel ridges, only visible under high 

 powers ; these ridges being suturally adapted to the correspond- 

 ing grooves or furrows of adjacent cells, thereby causing an 

 exceedingly firm union of the cells among themselves. 



§ 169. The second constant element in the structure of 

 epitheliomata is a stroma made up of connective tissue. Inas- 

 much as the bodies with which it shares the space assigned 

 to the entire tumour are of a cylindrical form, it must needs 

 constitute a honeycomb-like framework, the open ends of tlie 

 cells being directed outwards. The stroma consists at first of 

 the parenchyma of the cutis or mucous membrane dislocated and 

 frayed out. We learned on a former occasion (§ 83) to regard 

 the epithelium, apart from its first differentiation in the embryo, 

 as in every case a product of the connective tissue ; hence we 

 may take it for granted that the stroma plays a very active part 

 in epitheliomatous growth. We actually find, especially at those 

 points where the growth of the epithelial protrusions is most 

 active, that their apices are tipped with a luxuriant proliferation of 

 cells (c) ; the stroma is richly provided throughout with young 

 elements; moreover it is prone to take on an independent 

 activity, which usually leads to the development of papillary 

 excrescences. 



The stroma carries the vessels of the tumour ; they share its 

 fate in all respects ; when the stroma wastes, they are obliterated ; 

 when it developes a productive activity, they dilate (^see below). 

 Fig. 63 shows a successful injection of the vessels, executed 

 according to the directions given by Thiersch. 



§ 170. We come now to the degeneration of epithelial can- 

 cer. Its conditions are involved in the growth of the tumour 

 itself. Attention has already been called to the possibility of 

 the " pressure due to growth" interfering with the circulation, 

 and so disturbing nutrition in larger or smaller sections of the 

 tumour. These disturbances are first felt as a rule in such points 

 of the tumour as are already subjected to unfavourable nutritive 

 conditions. Such points are the centres of the epithelial protru- 

 sions. The thicker the protrusions, the farther their axial cells 

 are from the soil which gave them birth and which should 

 nourish them. The circumstance that these are the first-formed 

 and consequently the oldest cells operates in the same direction ; 

 so that we usually find the phenomena of retrograde meta- 



