426 INTRODUCTION TO CYTOLOGY 



without some reference to the early theories of preformation and 

 epigenesis. 



The Renewal of the Study of Organic Structure. — The researches of 

 Hooke, Grew, and Malpighi in the seventeenth century had made it 

 apparent that "cells," or "globules," are important structural elements 

 in organisms. When attention was again directed to such matters toward 

 the end of the eighteenth century, a number of interesting suggestions 

 were offered regarding the origin and significance of these elements. 



One of the earliest theories of cell-formation was that which had been 

 put forward by Wolff in his Theoria Generationis (1759). According, to 

 Wolff, every organ is at first a clear, viscous fluid with no definite struc- 

 tural organization. In this fluid, cavities ("Blaschen," "Zellen") arise 

 and become cells or, by elongation, vessels. These may later be thick- 

 ened by deposits from the " solidescible " nutritive fluid. The cavities, or 

 cells, are not to be regarded as independent entities: organization is not 

 effected by them, but they are rather the passive results of an organizing 

 force {vis essentialis) inherent in the living mass. 



K. Sprengel (1766-1833) stated that cells originate in the contents 

 of other cells as granules or vesicles which absorb water and enlarge. 

 This theory, in spite of its poor observational basis, was upheld by L. C. 

 Treviranus (1779-1864) in a work appearing in 1806, and both men 

 fought many years for its support. Kieser (1812) further developed the 

 idea that granules in the latex are "cell germs" which later hatch in the 

 intercellular spaces to form new cells. With a much clearer understand- 

 ing of the nature of the problems involved, a number of excellent observa- 

 tions were made by J. J. Bernhardi in 1805, by H. F. Link and K. A. 

 Rudolphi in 1807, and by J. J. P. Moldenhawer in 1812. It is to be 

 regretted that the deserved attention was not given to their results, for 

 they promised to lead in the right direction. 



Because of their relation to the cell theory, which is soon to be dis- 

 cussed, special consideration should be given the views of J. B. P. Lamarck 

 (1744-1829), C. F. Mirbel (1776-1854), and R. J. H. Dutrochet (1776- 

 1847). As emphasized by Gerould (1922), certain aspects of the cell 

 theory were taught in Paris at the opening of the nineteenth century, 

 40 years before the publication of the works which brought it into 

 prominence. 



The famous French biologist Lamarck, in his Philosophie Zoologique 

 (1809), strongly emphasized the fundamental importance of "cellular 

 tissue" in the structure and development of organisms. In his own 

 words, "... cellular tissue is the matrix in which all the organs of 

 living bodies have been successively formed, and . . . the movement of 

 fluids through it is nature's method of gradually creating and developing 

 those organs out of this tissue" (Elliott's translation, p. 230). He adds 

 in a footnote that he had been teaching this doctrine since 1796. By 



