364 



SCIENCE. 



[N. S. Vol. XII. No. 297. 



endogenous formation of cells to the carti- 

 lage cells in the process of inflammation 

 and to other tissues undergoing patholog- 

 ical changes. Corroborative observations 

 on endogenous formation were also given 

 by his brother Harry Goodsir in 1845. 

 These observations on the part which the 

 nucleus plays by cleavage in the formation 

 of young cells by endogenous development 

 from a parent center — that an organic con- 

 tinuity existed between a mother cell and 

 its descendants through the nucleus — con- 

 stituted a great step in advance of the views 

 entertained by Schleiden and Schwann, and 

 showed that Barry and the Goodsirs had a 

 deeper insight into the nature and functions 

 of cells than was possessed by most of their 

 contemporaries, and are of the highest im- 

 portance when viewed in the light of recent 

 observations. 



In 1841 Robert Remak published an ac- 

 count of the presence of two nuclei in the 

 blood corpuscles of the chick and the pig, 

 which he regarded as evidence of the pro- 

 duction of new corpuscles by division of the 

 nucleus within a parent cell ; but it was 

 not until some years afterwards (1850 to 

 1855) that he recorded additional observa- 

 tions and recognized that division of the 

 nucleus was the starting-point for the mul- 

 tiplication of cells in the ovum and in the 

 tissues generally. Eemak's view was that 

 the process of cell division began with the 

 cleavage of the nucleolus, followed by that 

 of the nucleus, and that again by cleavage 

 of the body of the cell and of its membrane. 

 Kolliker had previously, in 1843, described 

 the multiplication of nuclei in the ova of 

 parasitic worms, and drew the inference that 

 in the formation of young cells within the 

 egg the nucleus underwent cleavage, and 

 that each of its divisions entered into the 

 formation of a new cell. By these observa- 

 tions, and by others subsequently made, it 

 became obvious that the multiplication of 

 animal cells, either by division of the 



nucleus within the cell, or by the budding 

 off of a part of the protoplasm of the cell, 

 was to be regarded as a widely spread and 

 probably a universal process, and that each 

 new cell arose from a parent cell. 



Pathological observers were, however, for 

 the most part inclined to consider free cell- 

 formation in a blastema or exudation by an 

 aggregation of molecules, in accordance 

 with the views of Henle, as a common 

 phenomenon. This proposition was at- 

 tacked with great energy by Virchow in a 

 series of memoirs published in his 'Archiv,' 

 commencing in Vol. I., 1847, and finally 

 received its death-blow in his published 

 lectures on ' Cellular Pathology,' 1858. He 

 maintained that in pathological structures 

 there was no instance of cell development 

 de novo; where a cell existed, there one 

 must have been before. Cell-formation 

 was a continuous development by descent, 

 which he formulated in the expression 

 omnis cellula e cellula. 



KAETOKINESIS. 



Whilst the descent of cells from pre-exist- 

 ing cells by division of the nucleus during 

 the development of the egg, in the embrj'os 

 of plants and animals, and in adult vege- 

 table and animal tissues, both in healthy 

 and diseased conditions, had now become 

 generally recognized, the mechanism of the 

 process by which the cleavage of the nu- 

 cleus took place was for a long time un- 

 known. The discovery had to be deferred 

 until the optician had been able to con- 

 struct lenses of a higher penetrative power, 

 and the microscopist had learned the use 

 of coloring agents capable of dyeing the 

 finest elements of the tissues. There was 

 reason to believe that in some cases a direct 

 cleavage of the nucleus, to be followed bj' 

 a corresponding division of the cell into 

 two parts, did occur. In the period be- 

 tween 1870 and 1880 observations were 

 made by Schneider, Strasburger, Biitschli, 



