CELL AND PROTOPLASM CONCEPTS 



13 



Theodore Schwann (1810-1882), the 

 associate of Johannes Miiller at Wiirzburg 

 and Berlin and later Professor of Anatomy 

 at Louvain and Liege, took over the errone- 

 ous views of Schleiden as to cell genesis and 

 proceeded to apply these to animal cells. 

 Lamarck (1809), Dutrochet (1824), Tur- 

 pin (1826), Henle (1838), Purkinje (1833) 

 and Valentin (1836) had observed and de- 

 scribed animal cells and compared them 

 with plant cells, but only Dutrochet before 

 Schwann had taught that all the many 

 kinds of animal tissues are everywhere de- 

 rived from cells which are the elementary 

 type of organism. Schwann held that all 

 the different kinds of cells are morphologi- 

 cally related beause they all arise by the 

 same process, namely, as he mistakenly 

 supposed, from granules (nucleoli) which 

 become nuclei and which in turn give rise 

 to the cell body. Unlike Schleiden, he held 

 that this genesis could take place in a form- 

 less ground substance, the " cytoblastem, " 

 in spaces between cells, as well as within 

 mother cells "by a kind of crystallization 

 in a mother liquor." These erroneous 

 views persisted in botany for a long time 

 under the caption of ' ' free cell formation. ' ' 

 Fifty years ago I heard this idea presented 

 in lectures on general biology. 



The extra-cellular formation of cells was 

 opposed by many botanists and zoologists 

 soon after its proposal by Schwann.* Re- 

 mak held that such a mode of origin of cells 

 was as improbable as generatio aequivoca 

 of organisms and he proved in the case of 

 many animal tissues that new cells arise 

 only by division of preceding cells. In 

 1852, he extended this conclusion to patho- 

 logical tissues and tumors. Finally Vir- 



4 Schwann 's more enduring work was in physi- 

 ology rather than cell-studies. He made valuable 

 contributions on gastric digestion (he first named 

 pepsin) and on the function of gall. His study of 

 the anatomy of nerve fibers is still recognized in 

 the ' ' sheath of Schwann, ' ' and his work on the 

 contractility of arteries and on muscular contrac- 

 tility in general are worthy of mention. He fur- 

 nished evidence against the occurrence of spon- 

 taneous generation and in favor of the bacterial 

 cause of putrefaction; also that alcoholic fermen- 

 tation is caused by yeast, all of this some twenty 

 years before Pasteur's work on these subjects. 



chow (1859) is given the credit of forever 

 disposing of Schwann's hypothesis of free \ 

 cell formation, summing up this conclusion 

 in his dictum, "Omnis cellula e cellula." 



Schwann was the first to undertake a 

 comprehensive investigation of the general 

 tissues of the animal body and their de- 

 velopment out of cells. He first used the /| 

 term ' * cell theory ' ' for this conception : ' I 



The development of the proposition that there 

 exists one general principle for the formation of 

 all organic productions, and that this principle is 

 the formation of cells, as well as the conclusions 

 which may be drawn from this proposition, may be 

 comprised under the term Cell Theory. (Sydenham 

 Society translation, p. 166.) 



The work of Schwann formed the basis 

 of the theory of the "cell state," which 

 maintained that "cells are organisms and 

 that entire animals and plants are aggre- 

 gates of these organisms arranged accord- 

 ing to definite laws." This theory had a 

 long life and is still probably true in part, 

 but in its extreme form its inadequacies 

 were pointed out, in 1893, by Whitman and 

 by many experimental embryologists who 

 have called attention to the fact that both 

 in structure and function ' ' the organism as 

 a whole," is more than the sum of its cells 

 and that organization precedes cell forma- 

 tion and is not its product. 



In view of the fact that all discoveries are 

 based upon previous ones and that science 

 is possible only by such cooperation, I sug- 

 gest that it would be more accurate, as 

 well as more becoming, to strike out of our 

 literature these personal possession tags 

 attached to important discoveries in which 

 many persons have participated. And in 

 the case of the great generalization that the 

 bodies of animals and plants are composed 

 of cells and that these have all come by divi- 

 sion from preceding cells, it is absurd to 

 still speak of this as "the cell theory of 

 Schleiden and Schwann." 



III. Origin and Development of the 

 Protoplasm Concept 



In its beginning the cell theory paid little 

 attention to the cell contents and attributed 

 chief importance to the cell walls ; the cell 



