INTRODUCTION 9 



or of steel may well affect the durability and precision of the instrument, but 

 not the nature of its action. Similarly one cannot help assuming that the 

 mode of arrangement of the ultimate parts of the organism is of greater im- 

 portance than the chemical nature of these parts. 



Ernst Brucke (1861) deserves the credit of having been the first to lay 

 stress on the more minute structure of protoplasm as the cause of its vital 

 manifestations. He wrote in 1861 (p. 386), ' we are well acquainted with the 

 fact that the structure of the molecules of the organic substances which enter 

 into the composition of the cell is undoubtedly of a very complicated nature. 

 But we cannot rest content with simply postulating a complicated molecular 

 structure for the cell. It is impossible to think of a living vegetative cell as 

 consisting of merely a homogeneous nucleus . . . and a proteid solution, for we 

 certainly cannot perceive the phenomena which we term vital in the proteid 

 as such. On the contrary we are forced to ascribe to the living cell an entirely 

 distinct complexity of structure, quite apart from the molecular structure 

 of the organic compounds of which it is composed, and to this complexity 

 we may apply the term ' organization'. 



This organization demands special study, and for its investigation the 

 newest and strongest objectives must be employed. As, however, A. Fischer 

 (1899) has shown, investigations of this kind are certainly open to the possi- 

 bility of serious error, because those who aim at conducting research on proto- 

 plasm are compelled, from the nature of the case, to operate upon dead proto- 

 plasm ; since although great care be taken to preserve the natural structure in 

 killing and fixing the material, still very frequently artificially produced pre- 

 cipitates have been mistaken for genuine features of the protoplasm. 



According to many observers, protoplasm is composed of minute granules, 

 according to others it is made up of threads or netlike aggregations of fibrillae, 

 but all these theories of the structure of protoplasm are subject to the criticism 

 that they are based on an examination of dead and stained protoplasm and 

 not of the living substance. Butschli's (1892) alveolar theory of the structure 

 of protoplasm is free from this criticism, for undoubtedly there are many cases 

 where a structure may be seen in living protoplasm suggestive of that exhibited 

 by frothy liquids. [According to Fischer (Roux's Archiv f. Entwicklungs- 

 mechanik, Vol. 13, 1902) and especially A. Degen (Bot. Ztg. Vol. 63, 163, 

 1905), a foam-like structure in protoplasm is to be considered as a pathological 

 phenomenon.] But whether only the walls of the honeycomb-like spaces, lying 

 as they do at the limits of visibility, or their contents as well are to be con- 

 sidered as protoplasm it is impossible to say. It is equally certain that in 

 other cases no such alveolar structure can be determined in living protoplasm, 

 and thus we are forced to accept the views of Berthold (1886) and Fischer 

 (1899) as most in accordance with our present knowledge, viz. that the con- 

 stitution of protoplasm is neither uniform nor constant. Even if an alveolar 

 structure, in the sense understood by BtJxscHLi, could be demonstrated as of 

 general occurrence in protoplasm, we should not gain much thereby, for 

 BtJTSCHLi (1898) himself has shown that an alveolar structure may also be 

 demonstrated in dead bodies and so cannot be regarded as a definite character- 

 istic of living structure. 



Up to the present, then, the organization of protoplasm has not been un- 

 ravelled, although the investigations which have been carried out in this relation 

 have done much to render clearer our conception of what protoplasm really is. 

 No one nowadays doubts that it has a very complex structure, and we know 

 that it cannot any longer be considered as a homogeneous solution. Further, 

 no one expects to meet with the same or even an analogous structure in proto- 

 plasm as in a machine, the comparison of protoplasm with which must mani- 

 festly not be pressed too far. Owing to the manifold nature of the work 



