36 POPULAR SCIENCE MONTHLY. 



named by him idioplasm, extended throughout the whole of the plant, 

 forming its specific molecular constitution, and that growth and activity 

 were regulated by its conditions of tension and movements (1884). 



The study of the structure of plants, with special reference to the 

 presence of an intercellular network, has for some years been pursued by 

 Walter Gardiner (1882-97), who has demonstrated threads of cell plasm 

 protruding through the walls of vegetable cells and continuous with 

 similar threads from adjoining cells. Structurally, therefore, a plant 

 may be conceived to be built up of a nucleated cytoplasmic network, 

 each nucleus with the branching cell plasm surrounding it being a cen- 

 ter of activity. On this view a cell would retain to some extent its in- 

 dividuality, though, as Gardiner contends, the connecting threads would 

 be the medium for the conduction of impulses and of food from a cell 

 to those which lie around it. For the plant cell, therefore, as has long 

 been accepted in the animal cell, the wall is reduced to a secondary posi- 

 tion, and the active constituent is the nucleated cell plasm. It is not 

 unlikely that the absence of a controlling nervous system in plants re- 

 quires the plasm of adjoining cells to be brought into more immediate 

 contact and continuity than is the case with the generality of animal 

 cells, so as to provide a mechanism for harmonizing the nutritive and 

 other functional processes in the different areas in the body of the plant. 

 In this particular, it is of interest to note that the epithelial tissues in 

 animals, where somewhat similar connecting arrangements occur, are 

 only indirectly associated with the nervous and vascular systems, so that, 

 as in plants, the cells may require, for nutritive and other purposes, to 

 act and react directly on each other. 



NERVE CELLS. 



Of recent years great attention has been paid to the intimate struc- 

 ture of nerve cells, and to the appearance which they present when in 

 the exercise of their functional activity. A nerve cell is not a secreting 

 cell — that is, it does not derive from the blood or surrounding fluid a 

 pabulum which it elaborates into a visible, palpable secretion charac- 

 teristic of the organ of which the cell is a constituent element, to be in 

 due course discharged into a duct which conveys the secretion out of 

 the gland. Nerve cells, through the metabolic changes which take place 

 in them, in connection with their nutrition, are associated with the pro- 

 duction of the form of energy specially exhibited by animals which 

 possess a nervous system, termed nerve energy. It has long been known 

 that every nerve cell has a body in which a relatively large nucleus is 

 situated. A most important discovery was the recognition that the 

 body of every nerve cell had one or more processes growing out from it. 

 More recently it has been proved, chiefly through the researches of 

 Schultze, His, Golgi and Ramon y Cajal, that at least one of the pro- 



