THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM. l09 



iliforme" appearance leads one to suppose that the transformation into epidermal 

 fibrils takes place in several places in the substance of a single chondriokont. Ac- 

 cording to him, the fibrils are at first basophile, become acidophile, and are finally 

 masked, the whole cell assuming a homogeneous aspect. In the preparations which 

 he fixed in Meves's fluid and stained with either iron hematoxylin or krystallviolett, 

 both the mitochondria and the fibrils were stained. He writes (p. 542) that as 

 one examines the cells of more and more superficial layers of the corps muqueux 

 inferieur, one sees part of the chondriosomes elongate and assume an undulating 

 appearance; in the same cells other chondriosomes retain their primary dimensions. 

 The latter become less and less numerous as one approaches the corps muqueux 

 inferieur. 8oon almost all the chondriosomes have assumed the form of long 

 undulating filaments, which he says undoubtedly constitute the first-formed 

 epidermal fibrils. Since he found that the number of completely formed fibrils 

 in a cell greatly exceeds the original amount of mitochondria, he concludes that 

 the fibrils formed by the transformation of chondriosomes multiply by longitudinal 

 division, although neither he nor Branca observed it. He bases this conception 

 on two considerations: (1) that isolated epidermal fibrils are generally of finer 

 diameter than the chondriokonts; (2) that the division of other fibrillar formations 

 such as myofibrils and neurofibrils is admitted by most authors. 



Duesberg's observations on the epidermis of the tadpole lead him to the same 

 conclusion that the epidermal fibrils arise by the transformation of mitochondria 

 (1912, p. 796). 



Since the iron-hematoxylin method and the Benda method color the mito- 

 chondria and the completely formed fibrils (two very different structures micro- 

 chemically) alike, these methods of technique can not be regarded as suitable for 

 an investigation of this nature. More specific methods must of necessity be em- 

 ployed. It follows that Firket, in his series showing a parallelism between the 

 disappearance of mitochondria and the formation of fibrils, has had to rely solely 

 upon the diameter of the filaments to determine whether they are mitochondria 

 or differentiated fibrils. His position is therefore insecure, since he can not dis- 

 tinguish with certainty the structures between which he claims to show tran- 

 sitions. If we admit that this parallelism does exist, we find that it is capable of a 

 similar explanation to that advanced in the discussion of collagenic fibrils and 

 myofibrils, namely, that the amount of mitochondria is diminished because the 

 activity of the cells is lessened in the later stages of cytomorphosis. 



The problem is rendered more difficult and deceiving because of the superficial 

 resemblance which obtains between the stauiing reactions of the mitochondria 

 and of the fibrils. Some of the fundamental differences which are said to exist 

 between them may be indicated : 



Mitochondria. Fibrils. 



1. Granules, rods, filaments. Long threads of finer diameter (Firket, p. ,'544). 



2. Soluble in fluids containing an excess of acetic acid, Resistant to acetic acid in fixatives. 



e. g., Zenker's fluid. 



3. Destroyed by fixation in Bouin's fluid (Firket). Well preserved by Bouin's fluid (Firket). 



4. Acidophile in pancreas after fixation in non-mordanting First basophile, becoming later acidophile (Firket, 



fluids (Bensley, 1911, p. 362). p. 539). 



