Guilliermond - Atkinson — 20 — Cytoplasm 



late or alveolar structure. These fixatives, furthermore, have the 

 disadvantage of dissolving the lipides, which are among the essen- 

 tial constituents of the cjrtoplasm. Reagents containing acid in a 

 very dilute state, i.e., the least acid fixatives, especially formalin, 

 act more gently. They transform the cytoplasm into a very finely 

 granular coagulate which preserves, in appearance at least, the 

 homogeneous aspect it has in the living state. 



In general, fixed cytoplasm stains only with acid anilin dyes 

 (eosine, erythrosine, light green, etc.). This distinguishes it from 

 the nucleus which stains with basic anilin dyes. The cytoplasm 

 for this reason is said to be acidophilic while the nucleus is baso- 

 philic. This affinity of the cytoplasm for acids is generally attrib- 

 uted to the fact that in the nucleo-proteins which compose it the 

 nucleic acids may be entirely saturated with simple proteins. These 

 nucleo-proteins thus are presumed to act as bases in regard to the 



acid dyes. 



The use of the method of staining material after fixation has 

 led many cytologists, contrary to the now classic description of 

 DUJARDIN, to believe in the existence of a special organization in 

 the cytoplasm. So for a long time the cytologists endeavored to 

 investigate this structure, either by fixed and stained preparations 

 or by direct observation of living cells, but they encountered two 

 great obstacles. By fixing the cells, they completely upset the 

 constitution of the cytoplasm which, as will be seen, is in a colloidal 

 state and coagulation images were induced. In the second place, 

 by tearing off the epidermis or by sectioning or cutting the tissue 

 in artificial media in order to observe living cells, alterations of 

 the cytoplasm were caused leading to its death. 



Cytologists who studied it did not, consequently, agree on the 

 structure of the cytoplasm and numerous theories were proposed of 

 which for historical interest, the principal ones will be summarized 

 here and in as brief a manner as possible : 



1. Reticular theory, according to which the cytoplasm is com- 

 posed of a network of anastomosing filaments immersed in a sub- 

 stance which is more fluid and less refractive (Hanstein, Reinke, 

 Strasburger, Carnoy, etc.). 



2. _ Filar theory, according to which the cytoplasm is composed 

 of a fluid mass in which are immersed filaments of more solid mate- 

 rial which are isolated one from the other (Flemming, Haber- 

 landt). 



3. Alveolar theory, which seems to have had the most adher- 

 ents and which is still advocated by some cytologists. According 

 to this theory, the cytoplasm is formed by an assemblage of small 

 alveoli pressed one against the other with walls which are more 

 compact than the more fluid substance within (Butschli, Crato). 



4. — Emulsion theory of KUNSTLER, according to which the 

 cytoplasm is composed of an infinite number of very small Protem 

 spheres with compact envelopes and semi-fluid contents. Accord- 



