24 AS REGARDS PROTOPLASM, ETC. 



chemical analogy shall assign intellect and vitality to the 

 molecular constituents of the protoplasm, in connection with 

 which they are at least exhibited, 



In order, then, to obtain a footing on the ground offered 

 us, the first question we naturally put is, What is Protoplasm ? 

 And an answer to this question can be obtained only by a 

 reference to the historical progress of the physiological cell 

 theory. 



That theoiy may be said to have wholly grown up since John 

 Hunter wrote his celebrated work On the Nature of the Blood, 

 etc. New growths to Hunter depended on an exudation of the 

 plasma of the blood, in which, by virtue of its own plasticity, 

 vessels formed, and conditioned the further progress. The 

 influence of these ideas seems to have still acted, even after a 

 conception of the cell was arrived at. For starting element, 

 Schleiden required an intracellular plasma, and Schwann a 

 structureless exudation, in which minute granules, if not indeed 

 already pre-existent, formed, and by aggregation grew into 

 nuclei, round which singly the production of a membrane at 

 length enclosed a cell. It was then that, in this connection, we 

 heard of the terms blastema and cyto-blastema. The theory of 

 the vegetable cell was completed earlier than that of the animal 

 one. Completion of this latter, again, seems to have been first 

 effected by Schwann, after Muller had insisted on the analogy 

 between animal and vegetable tissue, and Valentin had demon- 

 strated a nucleus in the animal cell, as previously Brown in the 

 vegetable one. But assuming Schwann's labour, and what 

 surrounded it, to have been a first stage, the wonderful ability 

 of Virchow may be said to have raised the theory of the cell 

 fully to a second stage. Now, of this second stage, it is the 

 dissolution or resolution that has led to the emergence of the 

 word Protoplasm. 



The body, to Virchow, constituted a free state of individual 

 subjects, with equal rights but unequal capacities. These were 

 the cells, which consisted each of an enclosing membrane, and 

 an enclosed nucleus with surrounding intracellular matrix or 

 matter. These cells, further, propagated themselves, chiefly by 

 partition or division; and the fundamental principle of the whole 

 theory was expressed in the dictum, " Omnis cellula e cellula" 

 That is, the nucleus, becoming gradually elongated, at last 

 parted in the midst ; and each half, acting as centre of attrac- 

 tion to the surrounding intracellular matrix or contained matter, 

 stood forth as a new nucleus to a new cell, formed by division 

 at length of the original cell. 



The first step taken in resolution of this theory was completed 

 by Max Schultze, preceded by Ley dig. This was the elimina- 

 tion, on the whole, of an investing membrane. Such membrane 



