MITQCHONDRIA IN TISSUE CULTURES 359 



Size of mitochondria 



The mitochondria vary so greatly in size (fig. 10) that were 

 it not for prolonged study of them and the use of a specific 

 vital stain such as Janus green it would be difficult to believe 

 that they all belong in the same class of granules. Even in a 

 single cell great variation occurs from very minute granules 

 which are scarcely visible to relatively large masses (figs. 4, 5, 9) . 



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10 



Fig. 10 Camera lucida drawings of- mitochondria of various sizes and shapes 

 from different cells and specimens; osmic acid vapor and iron hematoxylin; X 

 790 diam. 



Fig. 11 Endodermal cells from 3-day culture of allantois from a 7-day chick; 

 Bensley's aniline fuschsin methylene green stain; X 790 diam. 



Occasionally a cell is seen in which all the mitochondria appear 

 to be swollen up and much larger than those in the surrounding 

 cells (fig. 11). To what this is due is not known. 



A mitochondrium under observation frequently seems to change 

 in size as well as shape, but so far no micrometer measurements 

 have been made to determine this point. Definite increase in 

 size has frequently been seen, due to fusion of two granules to 

 form a larger granule or to fusion of rods into threads; and 

 occasionally all the mitochondria in the cell may become col- 



