220 ON THE IDENTITY OF STRUCTURE OF PLANTS AND ANIMALS 



grows, and, as the primordial utricle, attains a large comparative size ; 

 — while in the Animal the Endoplast remains small, the principal bulk 

 of its tissues being formed by the periplastic substance ; and, 2 ; in 

 the nature of the chemical changes which take place in the periplastic 

 substance in each case. This distinction however does not always 

 hold good, the Ascidians furnishing examples of animals whose 

 periplastic substance contains cellulose. 



" The Plant, then, is an Animal confined in a wooden case, and 

 Nature, like Sycorax, holds thousands of ' delicate Ariels ' imprisoned 

 within every Oak. She is jealous of letting us know this, and among 

 the higher and more conspicuous forms of Plants, reveals it only by 

 such obscure manifestations as the shrinking of the Sensitive Plant, 

 the sudden clasp of the Dioncea, or, still more slightly, by the 

 phenomena of the Cyclosis. But among the immense variety of 

 creatures which belong to the invisible world, she allows more liberty 

 to her Dryads ; and the Protococci, the Volvox, and indeed all the 

 Algae, are, during one period of their existence, as active as animals 

 of a like grade in the scale. True they are doomed eventually to 

 shut themselves up within their wooden cages and remain quiescent, 

 but in this respect they are no worse off than the Polype, or the 

 Oyster even." 



In conclusion, the Lecturer stated his opinion that the Cell-theory 

 of Schwann consists of two portions of very unequal value, the one 

 anatomical, the other physiological. So far as it was based upon an 

 ultimate analysis of living beings and was an exhaustive expression 

 of their anatomy, so far will it take its place among the great advances 

 in Science. But its value is purely anatomical, and the attempts 

 which have been made by its author, and by others, to base upon it 

 some explanation of the Physiological phenomena of living beings by 

 the assumption of Cell-force, Metabolic-force, &c., &c., cannot be said 

 to be much more philosophical than the old notions of "the actions of 

 the vessels," of which physiologists have lately taken so much pains to 

 rid themselves. 



" The living body has often, and justly, been called, ' the House 

 we live in ; ' — suppose that one, ignorant of the mode in which a 

 house is built, were to pull it to pieces, and find it to be composed of 

 bricks and mortar, — would it be very philosophical on his part to 

 suppose that the house was built by bt'ick-force ? But this is just 

 what has been done with the human body. — We have broken it up 

 into 'cells,' and now we account for its genesis by cell-force." 



