64 

 points of view will have to be taken into account. 



In regard to the cell-material from v-hich the hyper- 

 trophied elements are derived various cases are conceivable: 

 cells of the most varied kinds, belonging to the most var- ' 

 ied tissue forms, epidermis, bark, mesophyll, vascular 

 bundle cells, etc, furnish hypertrophies, in short, all 

 cells which are still alive and whose membrances are still 

 capable of growth, can hypertrophy: as is well-laiown, lig- 

 nigied membranes achieve no further surface growth. 



Various possibilities are- conceivable also in the pro- 

 duction of abnormally large elements, just aS before in the 

 discussion of abnormally small cells ;- 



a. Either the hypertrophied cells are derived 

 from meristematic elements Tvhich, under normal con- 

 ditions, would have divided further, in which case 

 hypertrophies are indeed produced by a continued 

 gro?/th of the cells, but with no further division, 

 or only a tardy division takes place of such kind 

 that larger daughter cells arise than under normal 

 conditions: 



b. Or cells are involved which continue longer 



or more intensively than under normal conditions the 

 growth in length which follows the last division. 



c. Or cells of a permanent tissue are concerned, 

 which have previously ended their normal growths and 

 are excited to a subsequent increase by certain 

 external factors. 



It is not always easy to decide in detail to which of 

 the growups here named the different kinds of hypertrophies 

 belong. The qualities of the abnormally large cells them- 

 selves never throw light upon the kind of tissue-elements, 

 to which they may be graced back ontegenetioally. In the 

 over- whelming majority of cases, those mentioned second are 

 involved. Obviously, the most important difference between 

 the two modes is that the participating growth is abnormal 

 only in the second case; in cases of the first kind, the 

 febnormality lies alone in the omission of cell-division. 

 Since we have already characterized hjrp^rtrophy as an "ab- 

 normal process of growth" , it follows that strictly speak- 

 ing v/e are not concerned in these with hypertrophies,- that 

 therefore abnormally large cells can also be produced other- 

 wise than by hypertrophy, nevertheless, on account _ of the 

 external, correspondence with products ox hsrpertrophical 

 growth, examples of the first named mode of development must 

 be discussed in the present chapter. 



We will now fix our attention upon the process of growth. 

 The coefficient of increase is either equally large in all 

 directions, or some special direction of grov^rth may be re- 

 cognized. In the first case, the old proportions of the 

 (67) cell changed hypertrophically will remain; the hypertrophied 

 cell will Show an enlarged picture of the normal so far as 

 its form is regarded. In the second case, the proportions 

 will be changed in some v/ay, and a formal change in value 

 must appear; for instance, a sac-like cell will come from a 



