4 THE GENERAL CHARACTERS OF CELLS, BY S. STRICKER. 



investigations between sarcode and the protoplasm of the plant 

 on the one hand, and of animal cells on the other, under- 

 taken by E. Briicke* E. Hackel,f Max Schultze,} and W. 

 Kiihne, have, in a very short space of time, advanced our 

 knowledge on these points to a greater extent than the inves- 

 tigations of the preceding twenty years. 



Briicke, who regards the cells as elementary organisms, ad- 

 mirably expresses the ideas, the development of which has been 

 lightly sketched in the following passage : 



" If we consider," he says, " how complicated the mechanical 

 arrangements must be which lie at the root of the spontaneous 

 movements of cells, and if we consider further that up to the 

 present time we have only paid attention with the microscope 

 to obvious and perceptible movements, and that no regard has 

 been paid to the arrangements, by virtue of which the little 

 organism nourishes itself, increases in size, and begets its like, 

 nor any to those means by which it displays its specific 

 attributes ; if we, I say, consider all this, we must necessarily 

 recognise that we have to deal here with an organism, the 

 complication of which, although, truly, not comparable with 

 that of an animal, nor affording any good reason for believing 

 that it is itself composed of innumerable small organisms, yet 

 constitutes one to which we may fairly attribute the possession 

 of a highly artificial structure, the essential architectural 

 elements of which are, however, completely beyond our grasp." 



IDEAL TYPE OF A CELL. Johann Miiller proved that the 

 cells of the chorda dorsalis possessed proper walls. In similar 

 cells from the frog, Schwann demonstrated the existence of a 

 nucleus, and was by this discovery first led to perceive the 

 analogy between the cells of animals and plants. Here, then, 

 we have a cavity bounded by walls, in the interior of which 

 is a nucleus. 



Scarcely any structure is to be met with in the whole range 



* Elementar-organismen, Wiener Sitzungsberichtc, 1861. 



t Loc. cit. 



J Protoplasm der Rhizopoden. Leipzig, 1863. 



Protoplasma und die Contractilitdt. Leipzig, 1864. 



