CYTOPLASMIC CONSTITUENTS OF NERVE CELLS 413 



(4) The argument from analog}' is based on the development 

 of myofibrils, connective tissue fibrils and epidermal fibrils from 

 mitochondria according to the following observers. 



Benda ('99) and Meves ('07) were among the first to come to 

 the conclusion that mitochondria become changed into myofi- 

 brils. Duesberg wrote an excellent paper in 1910 in which he 

 supported theii" conclusion. In a subsequent contribution ('12, 

 p. 745) he states that while the two above named works (those 

 of Aleves and Hoven) render the plastochondrial (mitochondrial) 

 origin of collagenous fibrils and of nerve fibrils only probable, 

 the study of the fate of plastosomes (mitochondria) in myoblasts 

 permits their role in the formation of myofibrils to be shown un- 

 questionabl}-. I do not, however, feel ready to accept Duesberg's 

 evidence until I ha\'e satisfied myself that the similarity which 

 he found in the staining reactions of mitochondria and m^^ofibrils 

 by the Benda method is indicative of like chemical composition. 

 It is necessary for us to bear in mind that all structures which 

 stain alike by a single method are not necessarily of the same 

 nature. This similarity in staining is the only evidence which 

 he brings forward to prove the existence of microchemical tran- 

 sitions between mitochondria and myofibrils. It remains to be 

 proved whether it is sufficient or not. 



Aleves ('10) has studied the origin of connective tissue fibrils 

 in the tendons of chick embryos. The technique employed con- 

 sisted of fixation in his modification of Flemming's fluid, stain- 

 ing with iron hematoxjdin for mitochondria and of counter- 

 staining the fibrils with acid fuchsin. He found that the fibrils 

 first appear in the peripheral portions of the cells where the mito- 

 chondria are abundant and have become elongated, and claimed 

 to have established a quantitative relation between the increase 

 in the number of fibrils and the decrease in mitochondria. He 

 concluded that the connective tissue fibrils are formed by a mod- 

 ification of mitochondria. Since he has failed to show a grada- 

 tion between the black stained mitochondria and the brilliant red 

 colored fibrils, he assumes (p. 164) that there is a time when the 

 mitochondria change their chemical character so that the}^ can- 

 not be stained bv either iron hematoxvlin or acid fuchsin, that 



