THE STORY OF NINETEENTH-CENTURY SCIENCE 



spending similarity in the branchial cartilage of a tad- 

 pole. Then, too, the researches of Friedricli Henle had 

 shown that the particles that make up the epidermis of 

 animals are very cell-like in appearance. Indeed, the 

 cell-like character of certain animal tissues had come to 

 be matter of common note among students of minute 

 anatomy. Schwann felt that this similarity could not 

 be mere coincidence, but he had gained no clew to 

 further insight until Schleiden called his attention to 

 the nucleus. Then at once he reasoned that if there 

 really is the correspondence between vegetable and ani- 

 mal tissues that he suspected, and if the nucleus is so im- 

 portant in the vegetable cell as Schleiden believed, the 

 nucleus should also be found in the ultimate particles of 

 animal tissues. 



Schwann's researches soon showed the entire correct- 

 ness of this assumption. A closer study of animal tis- 

 sues under the microscope showed, particularly in the 

 case of embryonic tissues, that "opaque spots" such as 

 Schleiden described are really to be found there in 

 abundance forming, indeed, a most characteristic phase 

 of the structure. The location of these nuclei at com- 

 paratively regular intervals suggested that they are 

 found in definite compartments of the tissue, as Schleiden 

 had shown to be the case with vegetables ; indeed, the 



O 



walls that separated such cell- like compartments one from 

 another were in some cases visible. Particularly was 

 this found to be the case with embryonic tissues, and 

 the study of these soon convinced Schwann that his 

 original surmise had been correct, and that all animal 

 tissues are in their incipiency composed of particles not 

 unlike the ultimate particles of vegetables in short, of 

 what the botanists termed cells. Adopting this name, 



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