Guilliermond - Atkinson — 22 — Cytoplasm 



equilibrium of the colloidal system which we now know cytoplasm 

 to be, and brings about more or less important alterations. It has 

 been demonstrated that the spherical and alveolar structures are 

 in reality the result of alterations of the chondriosomes which swell 

 and are transformed into little spheres and large vesicles. As foi 

 the filar and granular theories, it will later be seen that they rest 

 on facts exactly observed but wrongly interpreted. Since the pro- 

 posal of these hypotheses, our knowledge of the cytoplasm has been 

 greatly enriched by observations of the following types of material : 

 fungi observed in their medium of culture, leaves of aquatic plants 

 examined also in their own medium, membranaceous bracts of Iris 

 preserved from all alteration by their impermeable cuticle, and 

 organs of plants growing in Petri dishes. 



It is thus definitely demonstrated at the present time that the 

 cytoplasm is a homogeneous colloidal system. Its physical charac- 

 teristics will be studied further on. The method of fixation and 

 staining can not be used in the study of the cytoplasm itself, for 

 this gives only pictures of coagulation which furnish no idea what- 

 ever of its actual nature. However, modern cytological work 

 carried out either by special techniques called mitochondrial or by 

 direct observation of living cells, with or without vital staining, 

 has revealed the constant presence, in the cytoplasm of each cell, 

 of a chondriome and a system of vacuoles, constituents of which 

 we have already spoken and which will be the subject of the fol- 

 lowing chapters. 



