36 THE CELL DOCTRINE. 



case with the vegetable cell according to Schlei- 

 den. Thus is formed the animal cell according to 

 Schwann, and although its method is identical with 

 that of Schleiden, both as to endogenous and ex- 

 ogenous cell formation, we have quoted his own 

 paper, because he is plainly fuller, and more precise 

 in his descriptions. The object of each observer was, 

 however, the same with regard to the tissues studied; 

 the additional object of Schwann being to show that 

 all organisms, whether animal or vegetable, are formed on 

 a common principle, and that this principle is origin from 

 cells, that the various tissues of the plant and animal, 

 however simple or complicated, are all combinations 

 of these cells, modified in adaptation to the special 

 peculiarities of tissues. 



The conception of Schleiden was truly original, 

 though its application was less difficult in conse- 

 quence of the simplicity of vegetable tissues. The 

 conception of Schwann was easier, in being the re- 

 flection of that of Schleiden, while its application was 

 more difficult, in consequence of the great diversity of 

 animal tissues; so difficult that he acknowledged that 

 "there are some exceptions, or at least differences, 

 which are as yet unexplained." This need not sur- 

 prise us when we recollect that one of the ablest 

 modern exponents of the cell theory, admits the diffi- 

 culty of its application to some of the so-called higher 

 tissues.* Indeed, the careful reader of Schwann's 

 researches cannot but be surprised at the accuracy 

 of the observations of this histologist, nor can he 



* Virchow, Cellular Pathology, Chance's Translation. Am. 

 Edit., Philada. : 1863, p. 78. 



