Allgemeines 3 



divisions, exactly as in the early stages of reproductive tissue. The 

 resemblance may extend to the freqnent production of giant cells, a 

 common occurrence in each case. 



As cell multiplication proceeds, however, a change passes over the 

 cells themselves. The protoplasmic continuity, to which the „prickly" 

 character is due, becomes more or less obliterated, and the cells assume 

 that appearance of indifferent germ tissue so well known as a feature of 

 the Clements of which malignant growths are largely made up. But, in 

 addition to this, other important changes occur which seem to have 

 been generally overlooked. 



A varying number of cells, situated in a zone behind the growing 

 edge of the advancing neoplasm, may be observed to attain some- 

 what large dimensions. Each contains a nucleus that grows to a 

 considerable size. As the latter enter on a prophase of division, 

 it is recognised that the chromosomes, instead of appearing as 

 delicate thin rods or V's, which are split longitudinally, present the 

 appearance of short thickened loops or rings, closely resembling the 

 later prophase stages of the heterotype mitosis in the normal reproductive 

 tissues. What is still more significant is the fact that in these cells the 

 number of the chromosomes is obviously less than in the normal somatic 

 cells of the surrounding tissues. In many cases the authors determined 

 the numbers to be approximately halved as compared with those of the 

 latter. Furthermore, it is clear that the loops and rings characteristic 

 of this stage of the cellular development of the malignant growth are 

 arranged lengthwise on the spindle, and so are ultimately divided trans- 

 versely, exactly as in the corresponding heterotype mitosis of the 

 reproductive elements. 



Subsequent divisions that occur behind this zone appear to resemble 

 the somatic form, but retain a reduced number of chromosomes, just as 

 do the cells that arise from a parent cell that has once exhibited the 

 heterotype character. But irregularities of various kinds usually super- 

 vene; amitosis is of frequent occurrence, and the number of the chromo- 

 somes in those nuclei that may continue to divide mitotically often exhibits 

 irregularity. These facts do not, however, seriously affect our position, 

 for in many plants similar irregularities occur in post-heterotype cells 

 that are not destined to give rise to actual sexual cells. 



The above-described series of cellular and nuclear changes are not 

 confined to epitheliomata, but recur in an essentially similar manner in 

 carcinomata and sarcomata. 



It thus becomes evident that in a most important respect, the 

 various types of malignant growths present certain features which are 

 common to all, and that these features are similar to those to be obser- 

 ved in the process of differentiation of reproductive cells from the pre- 

 ceeding somatic tissue. The authors feel that the evidence justifies them 

 in deliberately correlating the appearance of these neoplasms with the 

 result of a Stimulus which has changed the normal somatic course of 

 cell development into that characteristic of reproductive (not embryonic) 

 tissue. 



They look , then, upon this transformation as representing the 

 immediate cause of the development of the malignant growth, but the 

 remote cause must be sought for amongst those various Stimuli, some 

 of which, e. g., continuous irritation, are known to favour their deve- 

 lopment. 



Malignant growths seem, furthermore, to be definitely separable 

 from benign tumors, inasmuch as in the latter the authors have never suc- 

 ceeded in discovering anything resembling the very characteristic nuclear 

 changes they have described above. Thus, inter alia, while they have 

 in the example of a polypoid papilloma observed a considerable number 

 of somatic mitoses with the füll (unreduced) number of chromosomes, 

 they have been wholly unable to find a Single instance of a heterotype 

 division, or anything indicating that a reduction in the number of chro- 

 mosomes had taken place. 



1* 



