290 TUMORS. 



constant normal regeneration makes good the wear and tear of normal 

 cell life. But here the capacity for multiplication in the cells is closely 

 confined to the requirements of the body. A definite physiological con- 

 trol is evident, similar in character to that under which in normal devel- 

 opment the amount of new tissue is limited and its adaptation to the 

 organism as a whole secured. 



Under normal conditions, furthermore, there may be a very large 

 new formation of tissue under special physiological excitation, as in the 

 mammary gland and the uterus in pregnancy. But here also the charac- 

 ter and amount and the functional capacity of the new tissue are strictly 

 limited and subservient to the welfare of the individual. 



Let us now turn from these normal new tissues to those which are 

 abnormal. We have already seen, especially in our study of inflamma- 

 tion, that new tissues may form even in considerable amount under 

 abnormal conditions, such as injury with subsequent repair; excessive 

 functional activity as in various hyperplasise ; and under circumstances 

 which involve a special and little understood persistent stimulus, as in 

 interstitial inflammations. But under these various conditions also the 

 tissue growth is local, typical in structure, usually limited in amount, 

 and in most cases appears measurably to accord in nature and distribu- 

 tion with the maintenance of the structural integrity and general welfare 

 of the individual. The new tissue, in other words, maintains under all 

 these varied conditions a definitely co-ordinated relationship to the body 

 as a whole. 



While it is as yet impossible to define tumors in such a way as abso- 

 lutely to distinguish them from such other new tissue formations as we 

 have just cited, they are in general characterized by such irregularity in 

 growth both in structure and extent ; by such a lack of relationship to 

 the functional requirements of the individual, ' by such an independence 

 of that subtle physiological restraint which limits cell growth and pro- 

 liferation in the normal body, that their distinguishing character is per- 

 haps best indicated by the word autonomy, or by the more striking sug- 

 gestions of the term cell-anarchy. The autonomous or independent 

 character of tumors, as has been very clearly formulated by Thoma, is 

 especially manifested in the distinct limitation of the growth at the start ; 

 in the tendency to variation in the structural type ; in various functional 

 aberrations of the new cells ; in their interference by compression or 

 otherwise with adjacent parts ; in their proneuess to multiply through 

 local or distant transplantation of cells ; and finally, in their liability to 

 various forms of degeneration and necrosis. 



The reason why we cannot more accurately characterize tumors in 

 distinction from other new tissue formations is chiefly because we do not 

 yet know what are their immediate excitants. To this subject we shall 

 presently return, but we must first look at the general characters of 

 tumors. 



1 An example of a certain physiological independence in tumors is seen in lipomata, 

 in which a large amount of fat tissue may persist in an ill-nourished individual whose 

 fat has otherwise almost wholly disappeared ; or in myomata of an extremely atrophied 

 uterus. 



