MITOCHONDRIA IN TISSUE CULTURES 345 



plasm and nucleus are not noticeably altered except for the 

 staining. 



B, F. Kingsbury ('12) states that according to Rawitz ('()7), 

 Kollarewsky ('87) and Eisen ('00) osmic acid does not i)reser\^e 

 nuclear details. So far as can be seen from our material the 

 living cell exhibits few nuclear details and even osmic acid vapor 

 differentiates more clearly the nuclear structures than they can 

 be distinguished in the living cell. 



The mitochondria are so well fixed by osmic acid vapor or 

 by a fixing solution which contains osmic acid that it has been 

 suggested that the mitochondria may be artifacts due to osmic 

 fixation. Vapor from strong formalin which has been carefully 

 neutralized (Mann '02 and also Bensley '11 recommend that 

 formalin be freed from acid by careful neutralization and redis- 

 tillation) gave good results in regard to fixation not only of the 

 mitochondria but of all cellular structures. Unfortunately, the 

 mitochondria did not stain well after formalin fixation. Iodine 

 vapor from a crystal of iodine often afforded good results in 

 regard to the spindle fibers and also the mitochondria, especially 

 so when followed by Bensley's anilin fuchsin, methylene green 

 stain, but iodine was an uncertain fixative. Osmic acid solu- 

 tions do not give as uniformly good results as the vapor. 



Any fixing solution which contained acid (acetic, hydrochloric, 

 sulphuric, etc.) proved useless as a fixative for tissue cultures. 

 The vapor from such acids coagulated the entire cell before 

 the fluid touched the preparations. The mitochondria rapidly 

 changed into small granular rings, which later were completely 

 lost in the coagulated network of cytoplasm. The nucleus lost 

 its homogenous finely granular structure and a coarse network 

 appeared. The nucleolus became a small round bod}-. This re- 

 sembles closely the usual textbook figure of a cell, which by 

 long association one has come to believe represents a cell but 

 which actually resembles the living cell not at all. 



When a living cell (fig. 2 a) was exposed to the action of 

 vapor from 2 per cent glacial acetic this coagulation effect was 

 soon apparent, as shown in figure 2 b. The cytoplasmic and 

 nuclear networks rapidly appeared while the mitochondria, which 



