Caiapter III —21— Physical Properties 



ing to this theory, these spheres and not the cell, constitute the 

 essential morphological units of living matter. 



5. — Granular theory of Altmann which assumes that the 

 cytoplasm is composed of a very great number of small bodies in 

 the shape of grains called bioplasts, isolated or united in small 

 chains, having the appearance of bacteria. These grains are con- 

 tained in a homogeneous ground substance. According to Alt- 

 mann, these bioplasts are morphological and physiological units 

 capable of division and of leading an independent life. They are 

 homologous to bacteria which themselves represent independent 

 bioplasts. 



Let it be added that some cytologists used to think that all 

 these structures might be encountered in a single cell and repre- 

 sented, in consequence, only functional states of the cytoplasm. Yet 

 the research of Henneguy, Schwakz, A. Fischer, Chodat, etc., 

 had shown much earlier that different fixatives produced as many 

 different structures and that most of the structures described in 

 the cytoplasm were only artifacts produced by the fixatives. 



Since 1908, the use of new fixation techniques called mitochond- 

 rial, producing less violent coagulation and a better conservation of 

 the lipides of the cell, has led cytologists to return to the old idea 

 of Dujardin and to conclude that the cytoplasm is homogeneous 

 but encloses in suspension small elements called chondriosomes. 

 Observations of Faure-Fremiet on living cells of Protozoa (1910), 

 ours in plant cells (1913, 1919) and, finally, observations com- 

 pleted on Metazoan cells by using tissue cultures (M. R. and W. H. 

 Lewis, G. Levi, etc.) have confirmed these results and shown that 

 the cytoplasm, examined under favorable conditions, always appears 

 as an homogeneous and translucid substance, containing in suspen- 

 sion numerous, slightly more refractive chondriosomes. While this 

 work was being done, the use of the ultramicroscope had led physi- 

 ologists to conclude, even as early as 1904, that the cytoplasm is 

 in a colloidal state and in 1908 Mayer and Schaeffer were able 

 for the first time to show that this cytoplasm always appears 

 optically empty under the ultramicroscope and presents the char- 

 acter of a fluid hydrogel. From that time on, therefore, there 

 could no longer be any question of any structure in the cytoplasm 

 other than that inherent in its physical constitution. 



All theories proposed for the structure of cytoplasm are there- 

 fore out of date today and are now of historical interest only. It 

 is easy to understand how fragile the cytoplasm is, now that its 

 colloidal state is known. Most fixatives bring about the disorgan- 

 ization of the chondriosomes by dissolving their lipides at the same 

 time that they cause a coagulation of the cytoplasm. This coagu- 

 lated state appearing as a network was responsible for the formula- 

 tion of the reticular theory. On the other hand, observation of 

 living material, necessitating most often cutting or tearing of the 

 tissue which is then examined in an artificial medium or under 

 imperfect conditions, produces a disturbance in the very delicate 



