MITOCHONDRIA IN PLANT AND ANIMAL CELLS. 217 



Guilliermond ('iy, p. 438) and the formation of fat as described 

 by Dubreuil ('13, p. 104$). Compare Figs. 25 and 26. 



Striking differences also obtain in the morphology of mito- 

 chondria in the different categories of nerve cells. Nicholson 

 ('16, p. 347) has found that they are usually filamentous, espe- 

 cially in the anterior horn cells and in the cells of the reticular 

 formation ; they are rod-like and granular in the large and small 

 cells of the Gasserian ganglion, and they occur in the form of 

 large irregular blocks in the cells of the trapezoid nucleus. 



( I I o o O 



25 26 



FIG. 25. Metachromatic corpuscles developing in mitochondrial filaments 

 (after Guilliermond, '130, p. 438). 



FIG. 26. Droplets of fat forming in mitochondrial filaments .(after Dubreuil, 

 13, p. 104). 



The greater polymorphism of animal cells, with regard to 

 their mitochondrial content, probably results from the fact that 

 their functions are more diversified, for they have a greater 

 variety of duties to perform under different conditions. Appar- 

 ently their distribution within the cell is more varied in animals 

 than in plants for the same reason (p. 212). The form of mito- 

 chondria is apparently independent of the degree of mobility of 

 the surrounding protoplasm. 



It is worthy of note that in developing tissues of both plants 

 and animals similar and parallel changes take place in the 

 morphology of mitochondria, at least in certain instances. In 

 the spores of plants and the egg cells of animals, they are usually 

 granular and sometimes filamentous; in the developing tissues 

 of the embryo they are usually filamentous and rarely if ever 

 granular. With the assumption of special functions on the part 

 of the cells in the different organs they change their form. Some 

 remain filamentous and acquire blebs (secreting cells), others 

 become more rod-like (muscle), still others granular, and 

 so on. 



A single cell may contain all the types of mitochondria which 

 have been enumerated. This is true for animals as well as for 



