56 



Anniversary Meeting. 



[Nov. 30, 



Hooke demonstrated its cellular structure, and by an interesting coin- 

 cidence he was one of the first to investigate, at the request, indeed, 

 of the founder of the Society, Charles II, the movements of the sensi- 

 tive plant Mimosa pudica — one of a class of phenomena which is still 

 occupying the attention of more than one of our Fellows. In attribut- 

 ing the loss of turgescence, which is the cause of the collapse of the 

 petiole and subordinate portions of the compound leaf which it supports, 

 to the escape of a subtle humour, he to some extent foreshadowed the 

 modern view which attributes the collapse of the cells to the escape of 

 water by some mechanism far from clearly understood — whether from 

 the cell- cavities, or from the cell- walls into the intercellular spaces. 



Hooke having shown the way, Nehemiah Grew, who was also 

 Secretary of the Royal Society, and Marcello Malpighi, Professor of 

 Medicine in the University of Bologna, were not slow to follow it. 

 Almost simultaneously (1671-3) the researches of these two indefati- 

 gable students were presented to the Royal Society, and the publication 

 of two editions of Malpighi' s works in London proves how entirely 

 this country was at that time regarded as the head quarters of this 

 branch of scientific inquiry. We owe to them the generalisation of 

 the cellular structure, which Hooke had ascertained in cork, for all 

 other vegetable tissues. They described also accurately a host of 

 microscopic structures then made known for the first time. Thus, 

 to give one example, Grew figured and described in several different 

 plants the stomata of the epidermis : — " Passports," as he writes, either 

 " for the better avolation of superfluous sap, or the admission of air." 



With the exception of Leeuwenhoek no observer attempted to make 

 any substantial addition to the labours of Grew and Malpighi for 

 more than a century and a h?lf , and however remarkable is the impulse 

 which he gave to morphological studies, the view of Caspar Wolff: in 

 the middle of the 18th century (1759), in regarding cells as the 

 result of the action of an organizing power upon a matrix, and not 

 as themselves influencing organization, were adverse to the progress 

 of histology. It is from Schleiden (1838) who described the cell as 

 the true unit of vegetable stiucture, and Schwann who extended this 

 view to all organisms whether plants or animals, and gave its modern 

 basis to biology by reasserting the unity of organization throughout 

 animated nature, that we must date the modern achievements of histo- 

 logical science. Seldom, perhaps, in the history of science has any 

 one man been allowed to see so magnificent a development of his ideas 

 in the space of his own lifetime as has slowly grown up before the 

 eyes of the venerable Schwann, and it was, therefore, with peculiar 

 pleasure that a letter of congratulation was entrusted by your Officers 

 to one of our Pellows on behalf of this Society on the recent occasion 

 of the celebration of the 40th anniversary of Schwann's entry into the 

 professorate. 



