2 THE GENEEAL CHAEACTERS OF CELLS, BY S. STEICKEE. 



the epidermis cells, as they become more superficial, increase 

 in diameter. An instance was thus given of increase without 

 the intermediation of vessels. Schwann* seized the various 

 analogies and points of relation between the cells of animals 

 and plants in a comprehensive and fundamental proposition. 

 Animal cells, he said, are completely analogous to vegetable 

 cells, and are quite as independent in their mode of growth. 

 The vessels of the animal body only cause variations in the dis- 

 tribution of the nutritious fluid. 



Joh. Miillerf at once and unreservedly adopted this proposi- 

 tion. His observation, that the works of Schwann were the 

 most remarkable that had hitherto appeared in the domain of 

 histology, certainly greatly aided the rapid acceptance they 

 everywhere obtained. 



Virchow had already compared the whole organism to a free 

 state, containing individuals endowed with equal privileges if 

 not with equal powers. The views entertained of the physio- 

 logical significance of the constituents of the tissues, and espe- 

 cially of the animal cells, became, in consequence, completely 

 modified. An impulse leading to the further extension of these 

 ideas resulted from the examination of the lower forms of 

 animal life. DujardinJ had discovered in the year 1835 a con- 

 tractile substance capable of movement in the lower animals, 

 to which he applied the name of sarcode. The singularly 

 interesting phenomena exhibited by the living sarcode has at- 

 tracted the attention of many observers, as Meyen, Huxley, 

 Max Schultze, and Joh. Miiller. It was regarded as limited to 

 the lower animals; and though destitute of nerves, the possession 

 of irritability was ascribed to it.[| Meyen's attempt to show 

 that the Infusoria were unicellular organisms was indeed 

 refuted, but it was admitted that a little mass of sarcode con- 

 stituted a living and independent being. 



* Mikroskopische Untersuchunyen, 1839. 

 t Jahresberichl, 1839. 

 | Annal. des Sci. Nat., Tom. vii. 



See the general literature of this subject in E. Hackel, Die Radiolarien, 

 1862. 



j| See Max Schultze's Organism d. Polythalamien, 1854. 



