344 HISTOLOGY OF THE MORBID PROCESSES. 



arranged in a manner usually quite unlike that of any normal 

 organ. 



In consequence of the numerous variations in tissue-production 

 which may participate in their development it follows that tumors 

 have a marked individuality, and that only certain types of more 

 frequent occurrence can be described. Departures from those types 

 will be met with in practice, and they must each be interpreted in 

 accordance with the insight which the observer can gain as to their 

 nature and tendencies. The more atypical the structure of a growth 

 i. e.j the more it departs from the structure of normal adult tissue 

 the less likely is it to prove benign ; the more highly cellular it is, 

 the more likely it is either to grow rapidly or to act injuriously upon 

 the whole organism : for its cells derive their nourishment from the 

 general system and throw upon it the task of eliminating their waste- 

 products. 



Tumors are subject to morbid changes comparable with those 

 affecting normal tissues. They may be the seat of inflamma- 

 tion, infiltrations, and degenerations. In fact, the more cellular 

 forms are exceedingly prone to degenerative changes, due probably 

 to a relative insufficiency of nourishment consequent upon their 

 rapid growth and active metabolism. It is quite likely that the 

 products of those degenerations, when absorbed into the system, 

 act injuriously upon the general health. 



The effects upon the nutrition of the body occasioned by the 

 presence of a tumor constitute that part of the clinical picture 

 which is known as " cachexia," and is most marked when the tumor 

 is malignant But cachexia is not necessarily a sign of malignancy, 

 and is not always present, even when the patient has a very malig- 

 nant form of tumor. The degree of malignancy is measured by the 

 rapidity of growth, the tendency to infiltrate surrounding tissues, and 

 the liability to metastasis, and these depend upon the reproductive 

 activity of the cells and the extent to which their formative activity 

 is displayed in the elaboration of firm intercellular substances. 

 Metastasis takes place when cells become detached from a tumor 

 and are conveyed to some other part of the body, w r here they find 

 conditions favorable for their continued multiplication. They then 

 produce secondary tumors, which usually closely resemble the pri- 

 mary growth to which they owe their parent-cells. 



It is evident that a microscopical study of a tumor may be 

 made the basis of pretty accurate estimates of its nature and ten- 



