MITOCHONDRIA IN PLANT AND ANIMAL CELLS. 



199 



be discovered in the other. The absence of very minute mito- 

 chondria, merging into the invisible, is of interest from the 

 point of view of an origin de novo through condensation; and the 

 polymorphism, in both the pea and the pancreas, makes plain 

 the hopelessness of any attempt to devise a system of individual 

 nomenclature, based upon morphology, to embrace all the forms. 

 Obviously the material selected permits of very close comparison. 

 I have taken precautions in the following experiments to 

 eliminate, as far as possible, chance variations due to incurrent 



FIG. 4. Selected mitochondria from acinus cells of the mouse, treated in exactly 

 the same way, showing similar polymorphism. (3,500 diameters.) 



experimental errors which would, however, in any event, be 

 likely to effect both tissues similarly (see p. 207). They were 

 fixed together in the same bottle, dehydrated together, cleared 

 together and embedded in the same block of paraffin together. 

 They were cut with the same sweep of the knife, mounted on the 

 same slide and stained at the same time. Many preparations 

 have been made and in each of them the dehydration, clearing 

 and embedding were carried on in the same way, so that the 

 results are comparable. The sections were stained with iron 



