MORBID GROWTH IN GENERxVL. 71 



widely and in various ways from the form originally common to 

 all — that of a nucleated lump of protoplasm ; the changes which 

 have resulted in their differentiation being connected with their 

 functional activity. Hence we find that in nearly every tissue 

 our series of productive metamorphoses sets out from a different 

 point. We cannot shut our eyes, however, to the constant recur- 

 rence of certain common features, by combining which we may 

 very well construct a general plan of cell-production cle novo. 



An increase in the number of nuclei is never absent in any 

 case of cell-development. It is in the highest degree probable 

 that this increase is due in every case to fission of the original 

 solitary nucleus. Over and over again has this fission of the 

 nucleus been observed. We possess a countless number of care- 

 ful descriptions, telling us how the nucleus becomes lengthened, 

 how it is narrowed at its middle, exhibiting an hourglass con- 

 striction or inflexion, until at length its halves separate from 

 one another, and two nuclei take the place of one (fig. 26). 



The nucleolus too seems occasionally to take 

 part in the process. Nucleoli with a central con- ' ^^' " ' 



striction, hourglass-shaped, and double, have been 

 repeatedly observed in , the large, vesicular nuclei 

 of cancer-cells, in which the behaviour of the 

 nucleolus admits of being clearly traced. It must 

 nevertheless be admitted that the actual occurrence 

 of fission has been comparatively seldom seen. 

 This is easily accounted for by the extraordinary 

 quickness with which the fission takes place. 

 According; to all observers who have been luckv 

 enough to see the phenomenon actually take place Cells showing 

 before their eyes in recent livins: cells, it is the fission of nu- 



1 n n All ^ • T 'J. c^^i- From a 



work of a few seconds. Add to this that it may carcinoma. 



begin repeatedly, only to recede again ; in which 



case the inflexion which has been formed is again effaced, until, 



after several abortive attempts, fission is completed suddenly, as 



though it were a task for the due execution of which repeated 



efforts were needed. The same remarks apply to the subsequent 



fission of the cell itself; in either case we must bear in mind 



the saying of an illustrious naturalist, to the effect that one 



positive observation carries more weight than any number of 



negative ones. 



§ 67. Another phenomenon, which usually accompanies fission 



