242 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- 
proaching 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 
ycars 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. 
