28 W. H. GILBURT ON THE STRUCTURE AND 



and hydrogen are united in the same proportion, viz., ten to sixteen 

 atoms."* Now if in nature's laboratory, from the same materials 

 in exactly the same proportions, substances so different, and cause 

 ing in us such varied sensations, are produced, by simply altering 

 the arrangement of the constituent atoms, can we doubt the pos- 

 sibility that an almost endless diversity may exist in the arrange- 

 ment of the elementary atoms of which protoplasm is built up ? 



But it would seem that there are other reasons why we should 

 look for structure in protoplasm, not only molecular, but of a 

 coarser sort. One of the chief characteristics of all protoplasm is 

 its contractility ; not merely a shrinkage or apparent decrease in 

 size, which sometimes occurs through loss of water, but that kind 

 of contractility which results in motion — motion which may be 

 regular like that of the muscles, or irregular like that of the 

 Amoebae. That this property exists in vegetable protoplasm as well 

 as in animal is well known. Examples of it are met with in the 

 phenomenon of cyclosis as seen in many hairs, in Vallisneria, &c, 

 but many which approach nearer in appearance to what we call 

 Amoeboid are not difficult to find. For instance, if the sac of Vau- 

 cheria be ruptured, and the protoplasm allowed to escape into 

 water, amoeboid movement is set up in it, and may continue for 

 some time. In the plasmodium of the Myxomycetes the same 

 phenomena are also shown in a remarkable manner, and in the cells 

 of the higher plants, when the protoplasm forms a somewhat thick 

 and dense parietal layer upon the wall, a wave may sometimes be 

 seen to travel along it, not a transposition of the protoplasm, but 

 simply a contraction and expansion which passes from one end of 

 the cell to the other. Now, as we watch these movements, we find 

 that it requires an effort of the mind to resist the impression that 

 behind them all there is volition of some kind, and also that there 

 must be some machinery by which these movements are effected. 

 As to the idea of ivill, that cannot for one moment be retained ; 

 but the presence or otherwise of structural elements, by the em- 

 ployment of which these contractions are brought about, is a ques- 

 tion which may well be at least considered. 



There is one feature about these movements which is very re- 

 markable, and which must have struck every observer, viz., the in- 

 definiteness of the course of contraction, and the readiness with 

 which it may be reversed or varied. If the protoplasm is abso- 



* " Drysdale's Protoplasmic Theory of Life," p. 179. 



