MITOCHONDRIA IN TISSUE CULTURES 353 



of transformations from one shape into another can be watched 

 in the Hving cell. 



Mitochondria of various shapes have been described by other 

 observers, and so definite did some of the shapes appear to be 

 that they were given various names, which today are without 

 much significance. Nevertheless, it is convenient to classify 

 mitochondria as follows (fig. 10). 



The degenerate mitochondria also show more or less definite 

 shapes (fig. 13). 



Mitochondria continually change shape as by bending in vari- 

 ous directions (fig. 3 a), or by shortening and thickening or 

 elongating and thinning (fig. 3 b) ; at times this thickening and 

 thinning seems almost like a pulsation along the length of the 

 mitochondrium. These various shapes of mitochondria are not 

 fixed or constant in any cell. Rods or threads may change into 

 granules; threads may fuse or branch into networks (fig. 3 d, 6, 7) ; 

 or granules may fuse to form larger granules (fig. 3 c). Degen- 

 erating mitochondria may separate into granules and vesicles 

 (fig. 13). 



Ring-shaped mitochondria are seldom found in these prepa- 

 rations. Occasionally a living cell may contain one or two large 

 or small ring-shaped mitochondria which rapidly change into 

 threads, rods or granules. A few fixed and stained preparations 

 show one or two cells at the periphery of a large growth which 

 contain ring-shaped mitochondria exclusively (fig. 4g). Kings- 

 bury ('11) has suggested the possibility that mitochondria which 

 contain a large amount of lipoid are reduced by osmic acid only 

 at the surface, and the central part later dissolves out, which 

 produces the appearance of rings. These ring-shaped mito- 

 chondria can hardly produce fat or lipoid droplets (Dubreuil 

 '11, '13) since they are seldom present in cells in which fat is 

 being formed. 



