1890.] NEW-YORK MICROSCOPICAL SOCIETY. 10 



means 'when these are not present ;" and (2.) "that the property 

 of vitality does not reside equally in the various organic struc- 

 tures requiring such different physical properties, but is 

 restricted solely to a universally-diffused, pulpy, structureless 

 matter, similar to that of the ganglionic nerves and to the gray 

 matter of the cerebro-spinal nervous system."" 



As Doctor Drysdale remarks, " the progress of physiological 

 knowledge from the time of Fletcher may be said to be bound 

 up in the history of the cellular theory, which may be con- 

 sidered practically to have begun in 1838." But, as stated by 

 Doctor Tyson, "it is evident that for some time prior to the 

 year 1838, the cell had come to be quite universally recog- 

 nized as a constantly recurring element in vegetable and animal 

 tissues, though as yet little importance had been attached to it 

 as an element of organization, nor had its character been 

 clearly determined."^ 



It is to be noted, however, that nearly all the earlier observers 

 dealt exclusively either' with animal or with vegetable cells. It 

 is probable that Schwann was the first to bring both animal and 

 vegetable worlds under a general theory of cell-formation and 

 growth ; although Oken, as far back as 1808, had declared that 

 " animals and plants are throughout nothing else than mani- 

 foldly divided or repeating vesicles." Oken, however, appears 

 to have been engaged wholly with the morphological resem- 

 blances between the elementary parts of animals and plants, 

 and, as Schwann himself remarks, "nothing resulted from such 

 comparisons, because they were mere similarities in figure 

 between structures which present the greatest variety of forms." 



In 1837'Schleiden had made his discoveries as to the process 

 of origination and development in vegetable cells and had, 

 previous to publication, laid his conclusions before Schwann. 

 In enumerating the substances composing the cell-contents 

 Schleiden referred to a semi-granular substance occurring in 

 irregular forms, having no internal structure, which was colored 

 brown by tincture of iodine, and which he proposed to call 

 mucus. He however distinguished another, still simpler mat- 



« "The Protoplasmic Theory of Life." By John Drysdale, M. D., F. R. M. S. 

 Loudon, 1874. 



=> "The Cell Doctrine: Its History and Present State." By James Tyson, M. D. 

 Philadelphia ; 2d. Edu., 18T8. 



