THE SCIENTIFIC SPIRIT IN GERMANY. 



195 



cerning the structure and growth of plants. About the and 



Schwann. 



same time Theodor Schwann l extended this theory to 

 animal organisms. A variety of circumstances combined 

 to make the announcement of the cellular theory, which 

 will always be associated with those two names, an epoch 

 in the history of scientific, indeed of general, thought. 



The historian of botany, Julius Sachs, describes the 

 publication of Schleiden's great work as a burst of day- 

 light, 2 and Du Bois-Reymond says : " In order to measure 

 the magical progress which it marks, one must have wit- 

 nessed the rise of the cellular theory, when it suddenly 

 spread daylight in the darkness of the hidden structure 



to be found among men of pure 

 science in Germany. Opposed to 

 the idealistic philosophy as a fol- 

 lower of Fries, and on the other side 

 to the dry systematisation of the 

 Linmcan school, he was the man at 

 once to broaden the scientific view 

 and to create a popular interest in 

 the " life of the plant "-world. The 

 titles of his two best known works 

 are characteristic, ' Die Botanik als 

 inductive Wissenschaf t ' (1842-45), 

 and his short-lived periodical (filled 

 with the labours of his equally im- 

 portant co -editor, Nageli), ' Zeit- 

 schrift fur wissenschaftliche Bo- 

 tanik.' 



1 Through the friendship of 

 Schleiden and Schwann (1810-82, 

 a pupil of Johannes W tiller and 

 professor at Louvain), two inde- 

 pendent courses of research and 

 scientific thought were brought to- 

 gether. Schleiden placed the "cell" 

 a term used before him by Hooke, 

 Malpighi, Grew, Wolff, Brown, and 

 Mirbel in the forefront of his de- 

 scription as the element of form 

 and as the origin of life, or as we 

 now express it as the morphologi- 

 cal and embryological unit, in the 

 plant. A similar series of great 



names, beginning with Bichat and 

 leading up to Johannes Miiller, 

 marks the studies of animal tissues. 

 Schwann, struck with the analogy 

 of Schleiden's nucleated cells and 

 similar structures which he had 

 observed in the notochord, con- 

 ceived and verified on a large scale 

 the idea ' ' that a common principle 

 of development exists for the most 

 different elemental parts of the 

 organism, and that the formation 

 of cells is this principle." This is 

 the beginning of the cellular theory, 

 which produced at once a recon- 

 struction of the whole of " general 

 anatomy" by Jacob Henle (1809- 

 85), and subsequently the " cellu- 

 lar pathology " of Rudolph Virchow. 

 As the latter has himself said, he 

 aims at the establishment of a gen- 

 eral biological principle, and thus 

 the discovery of Schleiden and 

 Schwann is characterised as the 

 transition from the " historical " to 

 the " biological" study of animated 

 nature. 



2 See Julius Sachs, ' Geschichte 

 der Botanik vom 16 Jahrh. bis 

 I860,' p. 203, and in many other 

 passages. 



