244 PROTOPLASM 



distinguish between phaneroplasm and cryptoplasm from the 

 viewpoint of their vital significance, then, discontinuity of the 

 former and active streaming of the latter suggest that crypto- 

 plasm, the continuous phase, is the more fundamental of the two. 



Fixed Material. — The advent of cytological technique, between 

 the years 1870 and 1890, proved a great impetus to the study of 

 protoplasmic structure and yielded much of value, even though 

 many of the ideas formulated at the time have had to be discarded. 



When cells are prepared for microscopic study, they are killed 

 by fixatives (alcohol, formaldehyde, etc.), stained with dyes, 

 and sectioned. Such treatment may result in artifacts — struc- 

 tures not existing in the normal living state — on the other hand, 

 the method may reveal preexisting structures which were not 

 visible in the optically undifferentiated, living protoplasm. 



There has long persisted in the minds of biologists the thought 

 that there must exist a continuous framework of some sort which 

 is the structural background of protoplasm. Life in a dispersion 

 (solution) of isolated units, no matter how complex the mixture, 

 is inconceivable. Both this theoretical concept and actual 

 observations on fixed and stained material gave support to the 

 presence in protoplasm of a structure variously described but in 

 each instance consisting of a meshwork or entanglement of fibers, 

 forming a three-dimensional net or sponge. The idea of con- 

 tinuity in protoplasmic structure is thoroughly sound and is 

 supported by ample evidence, though much, yet by no means 

 all, of the cytological support (based on fixed material) given 

 to it is faulty. 



The Fibrillar Hypothesis, — The fibrillar hypothesis, advanced 

 by Flemming and others, ascribes to protoplasm the structure 

 of an entanglement of fibrils. Flemming elevated these fibrillae, 

 as did Altmann his granules, above the lowly station of mere 

 structural units and viewed them, as the seat of the energies on 

 which life depends. The drawings of Flemming of connective 

 tissue, of Heidenhain of muscle and spinal ganglion cells, and 

 preparations of Strasburger (Fig. 123) depict a fibrillar structure. 

 Such a structure is characteristic of and visible in certain living 

 tissues. Ettisch, with the aid of dark-field illumination, finds 

 the construction of sinew to be that of an aggregation of minute 

 fibers (Fig. 124). The fibers of microscopic dimensions are 



