STRUCTURAL BASIS OF PROTOPLASM 



25 



whether simple or branching ("filar theory" of Flemming), and the 

 same view is widely held at the present time. The meshwork has 

 received various names in accordance with this conception, among 

 which may be mentioned reticulum, thirad-zuork, spcvigioplasni, niitouie, 

 filar substance} all of which are still in use. Under this view the 

 "granules" described by Schultze, Virchow and still earlier observers 

 have been variously regarded as nodes of the network, optical sec- 

 tions of the threads, or as actual granules (" microsomes ") suspended 

 in the network as described above. 



Widely opposed to these views is the " alveolar theory " of Biitschli, 

 which has won an increasing number of adherents. Biitschli regards 

 protoplasm as having a foam-like alveolar structure ("Waben- 

 struktur"), nearly similar to that of an emulsion (Fig. 10), and he 

 has shown in a series of beautiful experiments that artificial emul- 

 sions, variously prepared, may show under the microscope a marvel- 

 lously close resemblance to living protoplasm, and further that drops 

 of oil-emulsion suspended in water may even exhibit amoeboid changes 

 of form. To restate Butschli's view, protoplasm consists of separate, 

 closely crowded minute drops^ of a liquid alveolar substance suspended 

 in a continuous intcralvcolar substance, likewise liquid, but of different 

 physical nature. The latter thus forms the walls of closed chambers 

 or alveoli in which the alveolar drops lie, just as in a fine emulsion 

 the emulsifying liquid surrounds the emulsified drops. The appear- 

 ance of a network in protoplasm is illusory, being due to optical sec- 

 tion of the interalveolar walls or partitions as viewed at any given 

 focus of the microscope. As thus seen, the walls themselves appear 

 as fibres, while the "spaces of the network" are in like manner opti- 

 cal sections of the alveoli, the alveolar substance that fills them 

 corresponding to the "ground substance." As explained beyond,'^ 

 Biitschli interprets in like manner the radiating systems or asters 

 formed during cell-divison, the astral rays (usually considered as 

 fibres) being regarded as merely the septa between radially arranged 

 alveoli (Fig. 10). 



The two (three) general views above outlined may be designated 

 respectively as the fibrillar (reticular or filar) and alveolar theories 

 of protoplasmic structure ; and each of them has been believed by 

 some of its adherents to be universally applicable to all forms of 

 protoplasm. Beside them may be placed, as a third general view, 

 the granular theory especially associated with the name of Altmann, 

 by whom it has been most fully developed, though a number of 

 earlier writers have held similar views. According to Altmann's 

 view, which apart from its theoretical development approaches in 



1 See Glossary. 



2 Measuring on an average about .001 mm. in diameter. ^ Cf. p. iic. 



