CHAPTER XXIL 



TUMOURS. 



STRUCTURE AND CLASSIFICATION — MALIGNANT TUMOURS — MICROSCOPIC 

 ANATOMY DIVISIONS — SGIRRHUS OR HARD CANCER — SOFT CAN- 

 CERS COLLOID MEDULLARY MELANOSIS EPITHELIAL 



CANCER. 



Tumours are included in that class of diseases named hyper- 

 trophies or over-growths ; and all their varieties consist in 

 additions to the organized materials of the body, arising from an 

 excess of formative force ; but in the case of each kind of tumour 

 the mode is peculiar in which this excess is manifested. A 

 tumour differs from an inflammatory exudate in — 1st. That its 

 increase is of itself ; 2d. That it grows as a part of the body by 

 its own inherent force, depending on the surrounding parts for 

 little more than a supply of blood, from which it appropriates 

 its nourishment ; 3d. As a general rule a tumour increases con- 

 stantly, whereas an inflammatory exudation depends upon a 

 morbid state of the parts at or contiguous to it; and in- 

 creases in size only so long as the morbid action in the adjacent 

 parts continues. Tumours are divided by Paget into innocent, 

 malignant, and recurrent or intermediate groups. The distinction 

 between an innocent and a malignant tumour is not one of mere 

 visible structure, nor of the microscopic character of its cellular 

 elements, but of origin and vital properties. Formerly it was 

 thought that the cells of a malignant growth (cancer cells) had 

 some characteristic peculiarity by which they could be dis- 

 tinguished from those of any other tumour ; at one time it was a 

 "typical caudate form;" then cancer cells were those having 

 large eccentric nuclei ; or else they were mother cells, containing 

 one or more smaller ones. At the present time, however, the 

 question is more the source and origin of those cells than any 

 peculiarity in tlieir character ; and it is now believed that their 



