24 2 BIOLOGY AND ITS MAKERS 



apparently a concise statement of the cell-idea prior to 

 Schleiden and Schwann; but we know that it was not 

 founded on observation. Oken, as was his wont, gave rein 

 to his imagination, and, on his part, the idea was entirely 

 theoretical, and amounted to nothing more than a lucky guess. 



Haller's fiber-theory gave place in the last part of the 

 eighteenth century to the theory that animals and plants are 

 composed of globules and formless material, and this globular 

 theory was in force up to the time of the great generalization 

 of Schleiden and Schwann. It was well expounded by Milne- 

 Edwards in 1823, and now we can recognize that at least 

 some of the globules which he described were the nucleated 

 cells of later writers. 



The Announcement of the Cell-Theory. We are now ap- 

 p^oaching the time when the cell-theory was to be launched. 

 During the first third of the nineteenth century there had ac- 

 cumulated a great mass of separate observations on the mi- 

 croscopic structure of both animals and plants. For several 

 years botanists, in particular, had been observing and writing 

 about cells, and interest in these structures was increasing. 

 "We must clearly recognize the fact that for some time prior 

 to 1838 the cell had come to be quite universally recognized 

 as a constantly recurring element in vegetable and animal 

 tissues, though little importance was attached to it as an 

 element of organization, nor had its character been clearly 

 determined " (Tyson). 



Then, in 1838, came the " master-stroke in generaliza- 

 tion " due to the combined labors of two friends, Schleiden 

 and Schwann. But, although these two men are recognized 

 as co-founders, they do not share honors equally; the work 

 of Schwann was much more comprehensive, and it was he 

 who first used the term cell-theory, and entered upon the 

 theoretical considerations which placed the theory before the 

 scientific world. 



