THE BACTERIAL NATURE OF MITOCHONDRIA 37 



chondrial fixative. When these incubated tissues were 

 examined microscopically, it was found that the mito- 

 chondria had changed in morphology within the cell. The 

 pleomorphism here observed was identical with that noted 

 in the case of mitochondria grown on the surface of the 

 media in the previous experiments. Figures 1 to 12 on 

 plate II are camera lucida drawings of some of the organisms 

 that developed on the surface of the cultures. Figure 13 

 is a camera lucida drawing of a piece of normal unincubated 

 liver tissue from a rabbit showing the normal appearance of 

 the mitochondria. Figures 14 to 18 are similar drawings 

 of liver tissue from the same rabbit as shown in figure 13, 

 after being incubated in urea-liver media at 37.5°C. for 

 two, four, six, eight and six hours, respectively. It is 

 evident, after an examination of these figures, that the 

 mitochondria changed in morphology when the tissue was 

 incubated. It is also evident that the organisms that had 

 developed on the surface of the media are identical in 

 morphology with the pleomorphic mitochondria within the 

 incubated liver cells. 



The vagaries of contamination in bacterial work are a 

 veritable "bug-a-boo" to the investigator. The bacteri- 

 ologist has learned that error from contamination often 

 leads him astray in the search for truth. Sometimes he 

 traces the source of his contamination to the glassware 

 used, and which he had sterilized in the usual manner. In 

 other cases, the contamination, apparently, crept into the 

 media during the manipulations of planting. It seems to 

 me, that error from contamination is ruled out in this last 

 set of experiments. I have attempted to find some expla- 

 nation other than a mitochondrial origin for these organ- 

 isms. The tissues during explantation might possibly 

 become contaminated, but it is impossible to conceive of 

 such contaminating organisms penetrating to the interior 

 of cells in the deeper part of the tissue and multiplying to 



