204 EPITHELIAL CAPtCINOMATA. 



liiglily-developed squamous elements interiorly (just as in the 

 healthy cutis). These small cells fill up all crevices ; everything 

 is continuous, there are no breaks. And a tendency to concen- 

 trie lamination prevails throughout. 



We may fairly assume that inasmuch as the infiltrated 

 parenchyma is not capable of being stretched beyond a certain 

 point, the peg-sliaped protrusions cannot attain more than a cer- 

 tain definite thickness. Now supposing that new cells continue 

 to be formed it is clear that the available space must sooner 

 or later be exhausted ; pressure must arise in the interior of the 

 tumour, which will be exerted both on the processes themselves 

 and on the connective tissue of the intervening stroma. I 

 regard this " compression due to growth " as a very important 

 element in the life-history of all infiltrative growths ; for, in so far 

 as it compresses the interstitial vessels, it must hinder the circu- 

 lation of the blood, disturb the nutrition of the parts, and thus, 

 as a rule, be the prime cause of degenerative changes. This 

 part of its action is the same in epithelioma as in other tumours ; 

 I am inclined moreover to assign it a share in the tendency 

 towards lamination alluded to above, a tendency shown by the 

 cells in the interior of the epithelial protrusions, and which 

 culminates in the formation of the so-called " pearly globes or 

 nodules." 



The pearly globes are produced as follows (fig. 63) : at 

 intervals in the axis of the epithelial protrusions, one or two 

 cells which retain their spherical form, serve as a nucleus 

 to which the adjacent elements are applied like the con- 

 centric scales of a bulb ; these elements being flattened out, so 

 as to yield the optical effect of fine dark lines when seen edge- 

 ways, just as in the hairs and nails. Large numbers of cells 

 are thus squeezed into a small, globular space ; the entire mass 

 presenting a homogeneous, intensely yellow and lustrous aspect, 

 which recalls the colour of hair. Tlie individual nodules may 

 rrrow to a considerable size ; and we shall find in what is known 

 as '^pearly cancer" {see cysts of nervous organs, brain) a form 

 of epithelioma in which the entire tumour is ultimately converted 

 into an aggregate of pearly nodules. 



The cells of epithelioma are also liable to another interesting 

 change, which is not, however, common ; they may become 

 o-rooved. This term is applied to cells Avhose surface is beset 



