THE CELL THEORY 247 
tant work. Apart from that his best-known contributions to 
science are: experiments upon spontaneous generation, his 
discovery of the ‘‘sheath of Schwann,” in nerve fibers, and 
his theory of fermentation as produced by microbes. 
Schleiden.—Schleiden (Fig. 75) was quite different in 
temperament from Schwann. He did not have the fine self- 
control of Schwann, but was quick to take up the gauntlet 
and enter upon controversies. In his caustic replies to his 
critics, he indulged in sharp personalities, and one is at times 
inclined to suspect that his early experience as a lawyer had 
something to do with his method of handling opposition. 
With all this he had correct ideas of the object of scientific 
study and of the methods to be used in its pursuit. He in- 
sisted upon observation and experiment,and upon the neces- 
sity of studying the development of plants in order to under- 
stand their anatomy and physiology. He speaks scornfully 
of the botany of mere species-making as follows: 
“‘Most people of the world, even the most enlightened, are 
still in the habit of regarding the botanist as a dealer in bar- 
barous Latin names, as a man who gathers flowers, names 
them, dries them, and wraps them in paper, and all of whose 
wisdom consists in determining and classifying this hay 
which he has collected with such great pains.” 
Although he insisted on correct methods, his ardent nature 
led him to champion conclusions of his own before they were 
thoroughly tested. His great influence in the development 
of scientific botany lay in his earnestness, his application of 
new methods, and his fearlessness in drawing conclusions, 
which, although frequently wrong, formed the starting-point 
of new researches. 
Let us now examine the original publications upon which 
the cell-theory was founded. 
Schleiden’s Contribution.—-Schleiden’s paper was par- 
ticularly directed to the question, How does the cell originate ? 
