STRUCTURAL BASIS OF PROTOPLASM 21 



These studies have raised interesting problems regarding the signifi- 

 cance of the granules described by the early observers. Many of the 

 granules, especially the larger and more obvious of them, are unques- 

 tionably irt'ert bodies, such as reserve food-matters, suspended in the 

 meshwork. Others are nodes of the network or optical sections of 

 the threads. But there is some reason to believe that, apart from 

 these appearances, discrete living particles may form a constant 

 and essential structural feature of the protoplasmic thread. These 

 particles, now generally known as microsomes, 1 are embedded in the 

 threads of the network, and are sometimes so closely and regularly set 

 as irresistibly to suggest the view that they are definite structural ele- 

 ments out of which the thread is built. More than this, their behaviour 

 is in some cases such as to have led to the hypothesis long since 

 suggested by Henle ('41) and at a later period developed by Bechamp 

 and Estor, by Maggi and especially by Altmann, that microsomes are 

 actually organic units or bioblasts, capable of assimilation, growth, and 

 division, and hence to be regarded as elementary units of structure 

 standing between the cell and the ultimate molecules of living matter. 

 And thus the theory of genetic continuity expressed by Redi in the 

 aphorism " omne vivum ex vivo" reduced by Virchow to " omnis 

 cellula e cellula" finally appears in the writings of Altmann as "omne 

 granulum e granulo! " 2 



Altmann's premature generalization rests upon a very insecure 

 foundation and has been received with just scepticism. That the cell 

 consists of more elementary units of organization is nevertheless in- 

 dicated by a priori evidence so cogent as to have driven many of the 

 foremost leaders of biological thought into the belief that such units 

 must exist, whether or not the microscope reveals them to view. 

 Among those who have accepted this conception in one form or 

 another are numbered such men as Spencer, Darwin, Beale, Haeckel, 

 Michael Foster, Nageli, De Vries, Wiesner, Roux, Weismann, Oscar 

 Hertwig, Verworn, and Whitman. The modern conception of ultra- 

 cellular units, ranking between the molecule and the cell, was first 

 definitely suggested by Briicke ('6i), 3 only, however, to be rejected 

 as without the support of facts, though this eminent physiologist 

 insisted that the cell must possess a more complicated organization 

 than that revealed by the best microscopes of his time. It was soon 

 afterwards taken up by Herbert Spencer, and elaborated into the 

 theory of physiological units by which he endeavoured to explain 

 the phenomena of regeneration, development, and heredity. Darwin 



1 Hanstein ('82). 



2 Die Elenientarorganisnien, Leipsic, 1894, p. 155- 



3 For a review of speculations in the same direction by Buffon and other early writers see 

 Yves Delage ('9S) 



