THE STRUCTURE OF CELLS 



mere structureless jelly, but possessed an organisation of their own. 

 At first the recognition of this fact only appears in tentative sug- 

 gestions, and hardly any serious progress was made beyond the 

 obvious distinction of the nucleus from the protoplasm. Briicke 

 seems to have been the first to point out the philosophical necessity 

 of assuming an organisation in the protoplasm, but the visual per- 

 ception of the counterpart of such a constitution hardly advanced 

 beyond the recognition of a relatively solid mass bathed in a more 

 fluid substance. The former was distinguished as spongioplasm, 

 and the latter as hyaloplasm. It is significant of the difficulty 

 experienced in arriving at a definite decision on the then available 

 evidence that each of the two constituents has been claimed In- 

 different writers as the living substance. 



The views which have been put forward as to the relationships 

 of the various substances which co-exist in the protoplasm to each 

 other have developed in two principal directions. The earlier, his- 

 torically speaking, was advocated by Frommann in a series of papers 

 dating from 1864. He was led, by a study of nerves, to distinguish 

 a reticulum, which partly corresponds with Leydig's spongioplasm. 

 This reticulum was imbedded in a more homogeneous ground sub- 

 stance, which, however, includes much more than spongioplasm. 

 He extended this conception of protoplasmic structure to plant cells, 

 and it was utilised, and in some respects modified, by Heitzmann in 

 1873. The views of the latter author were not so convincing as 

 those of Frommann, for it is quite possible to identify the structures 

 described by the latter writer in living cells, although the appear- 

 ances are susceptible of a different interpretation from that given 

 by him. Heitzmann's descriptions, on the other hand, are very 

 schematic, and it is difficult to avoid the conviction that they are 

 highly coloured by theoretical preconceptions. The phenomena of 

 contraction and extension were brought by him in relation to the 

 structures as described, but his views have never met with very 

 general acceptance. A closely related hypothesis was that suggested 

 by Flemming, who, while denying the existence of a reticulum, 

 insisted on the presence of a fibrillar structure, the fibrils being 

 represented as threads of irregular length (the filar elements) which 

 were imbedded in a more fluid interfilar mass. 



Gradually another view of the structure of protoplasm was 

 evolved, and which, in a measure, took account of reticular structure, 

 but explained it differently. Strasburger in 1876 first seems to 

 have spoken of closed protoplasmic chambers, which were filled with 

 more fluid albumen, but he soon abandoned the idea in favour of 

 the reticular hypothesis. But the alveolar theory thus indicated 

 was developed and extended by Biitsclili, who had, as long ago 

 as 1873, figured in Pilidium a structure susceptible of such an 

 explanation, though this was not given at that time. The alveolar 



