A HISTORY OF SCIENCE 



Schwann's researches soon showed the entire cor- 

 rectness of this assumption. A closer study of animal 

 tissues 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 

 comparatively regular intervals suggested that they are 

 found in definite compartments of the tissue, as Schlei- 

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

 the walls that separated such cell-like compartments 

 one from another were in some cases visible. Par- 

 ticularly 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 par- 

 ticles not unlike the ultimate particles of vegetables 

 in short, of what the botanists termed cells. Adopting 

 this name, Schwann propounded what soon became 

 famous as his cell theory, under title of Mikroskop- 

 ische Untersuchungen iiber die Ubereinstimmung in der 

 Structur und dem Wachsthum der Thiere und Pflanzen. 

 So expeditious had been his work that this book was 

 published early in 1839, only a few months after the 

 appearance of Schleiden's paper. 



As the title suggests, the main idea that actuated 

 Schwann was to unify vegetable and animal tissues. 

 Accepting cell-structure as the basis of all vegetable 

 tissues, he sought to show that the same is true of ani- 

 mal tissues, all the seeming diversities of fibre being 

 but the alteration and development of what were origi- 

 nally simple cells. And by cell Schwann meant, as did 



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