140 THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM. 



fact mitochondria are just as abundant in rapidly growing tumors as in those of 

 the benign variety. This has been confirmed by G. Arnold (1912a, p. 283), Favre 

 and Regaud (1913, p. 688), Porcelli-Titone (1914, p. 237), and all the others who 

 have worked with malignant growths. 



A number of purely descriptive papers have appeared on mitochondria in 

 different varieties of tumors, chefly in human tissues taken at operation or autopsy. 

 No results of great importance have been achieved (see p. 135). Let us hope that 

 the work will take an experimental turn. Much remains to be done. One is 

 tempted to entertain, as a working hypothesis, the view that mitochondria may 

 serve, in a measure, as indicators of the effect of X-rays, radium, and other so- 

 called therapeutic agents on tumor cells. The isolated notes on mitochondria in 

 human tumors are all very well to begin with, but we must have detailed and 

 comprehensive accounts of mitochondria in some particular type of tumor in 

 animal cells before experiments can be profitably commenced. We want to know 

 the whole story of mitochondria from the origin of the tumor to the end. Another 

 prerequisite is some accurate information upon the effect of X-ray and radium upon 

 normal cells, because it appears that the results of Beckton and Russ (1911, p. 

 105) require confirmation. 



It would be interesting to compare the mitochondria in the cells of the crown 

 gall in jjlants with cancer cells in man to ascertain whether they present any points 

 of sunilarity or dissimilarity. The degree of resemblance between the two is of 

 prime importance in view of Erwin F. Smith's (1917, p. 277) discovery that crown 

 gall is caused by an infection wdth a specific organism and his suggestion that 

 cancer in man is Ukewise infectious. Moreover, tumors offer a new and attractive 

 field for the study of the behavior of mitochondria in histogenesis. Nobody has 

 even touched on the relations of the myofibrils in myomata, and of the connective- 

 tissue fibrils in fibromata to mitochondria, to say nothing of the fascinating 

 problems presented by the rarer types of neuromata. If there is such a thing as de- 

 differentiation in tumors, a study of the process might go far toward clearing up 

 the whole problem of the part played by mitochondria in normal differentiation, 

 for many chemical reactions are reversible; if the mitochondria form the large 

 variety of chemical substances which it has been claimed they do in normal differ- 

 entiation, then it is quite reasonable to suppose that they may be reformed from 

 these same materials, dedifferentiation taking place. 



