ALEXANDER BRAUN. 33 



proves this by showing that in Algae and fungi (nostoc, pal- 

 mella, &c.) the gelatinous intercellular mass was produced by 

 the cells not vice versd (135). 



We have thus, in 1846, an anticipation of some very impor- 

 tant principles whose application to animal physiology was only 

 recognized long afterwards. 



We turn next to the memoir of Alexander Braun, entitled 

 " On the Phenomena of Rejuvenescence in Nature," 1850, trans- 

 lated by the Ray Society, 1850. 



Alex. Braun follows Schleiden in holding the cell to be " the 

 simplest sphere of formation in the course of the life and 

 growth of the plant, from which all development starts, which 

 in infinitely varied repetition and modification accompanies the 

 entire development, and to the independent representation of 

 which the conclusion of the development once more returns " 

 (121). He thus describes the cell. 



" Examining the individual cell more closely, we must, in the 

 first place, observe that the term cell does not correspond 

 exactly to that to which we especially apply it, for we under- 

 stand as cells, not merely the membranous vesicles or utricles 

 which form the tissue, but also their contents ; we apply the 

 name cell, not alone to the little chamber formed by a com- 

 pletely closed-in wall, within which the vegetable life conceals 

 itself, but also to its living inhabitant, the more or less fluid 

 and inwardly mobile body, which is bounded within the cham- 

 ber by its more delicate coat (the primordial utricle). The cell 

 is thus a little organism, which forms its covering outside, as 

 the muscles, the snail, or the crab does its shell. The contents 

 enclosed by these envelopes form the essential and original 

 part of the cell ; in fact, must be regarded as a cell, before the 

 covering is acquired. From the contents issues all the physio- 

 logical activity of the cell, while the membrane is a product 

 deposited outside, a secreted structure, which only passively 

 shares the life, forming the medium of intercourse between the 

 interior and the external world, at once separating and com- 

 bining the neighbouring cells, affording protection and solidity 

 to the individual cell in connection with the entire tissue. 

 Hence the development of the cell coat, as a product of cellular 



3 



