THE STUDY OF STRUCTURE. 361 



stance varies in different cells and even at different 

 times within the same cells. The investigations of 

 Biitschli, who has studied the structure of fine arti- 

 ficial emulsions and compared this with that of cells 

 both fixed and living, who has also investigated the 

 fine structure of dead organic substances like cellu- 

 lose, starch grains, chitinous shells, spicules, etc., 

 mark at present the extreme of microscopical analy- 

 sis. It is interesting to note that all his results 

 favour the interpretation that the complexity is 

 alveolar or vacuolar like that of a very delicate emul- 

 sion. Better lenses, thinner sections, differential 

 staining, and other improvements in technique have 

 led to the disclosure of a complexity undreamt of 

 half a century ago. The contrast between the mod- 

 ern analysis of a spermatozoon or of a cilium and 

 that of even a quarter of a century ago is most 

 vividly illustrative of the increased precision. If any 

 one name may be associated with the recognition of 

 complex cellular organisation, it should be that of 

 Briicke, whose classic work entitled Die Elementar- 

 organismen was published in 1861. But even if we 

 have succeeded, at length, in getting down to the 

 ultimate elements of living matter, or " idiosomes," 

 in which some believe that the secret of organisation, 

 growth, and development lies hidden, we have to 

 hand on the problem of their nature to the twentieth 

 century still unsolved. " What these idiosomes are, 

 and how they determine organisation, form, and dif- 

 ferentiation, is the problem of problems on which 

 we must wait for more light. All growth, assimila- 

 tion, reproduction, and regeneration may be sup- 

 posed to have their seats in these fundamental ele- 

 ments. They make up all living matter, are the 



