ON THE NATURE OF MITOCHONDRIA 453 
Figure 7 is a camera-lucida drawing of a part of a rabbit-liver 
smear after pyronin-methyl-green staining. The small stained 
bodies in this preparation appear like the typical mitochondria 
of liver cells. I can find no alibi for their mitochondrial nature. 
Figure 8 is a camera-lucida drawing of a portion of a rabbit- 
kidney smear after pyronin-methyl-green staining. It is difficult 
to find a place in the kidney smears where mitochondria-like 
bodies are distinct or present. The group of kidney cells illus- 
trated was more or less intact. The minute bodies in the illus- 
tration were sharply differentiated and are not unlike the typical 
kidney mitochondria. 
Figure 9 is a camera-lucida drawing of a part of a rabbit 
lymph-node smear after pyronin-methyl-green staining. The 
minute bodies represented in the illustration were sharply differ- 
entiated not only in the cells intact, but also in the cytoplasm of 
ruptured cells. They appear like the typical lymph-node mito- 
chondria. 5: 
In a number of lymph-node-smear preparations it was observed 
that in some cells the entire cytoplasm, which was apparently 
intact, was homogenously stained with pyronin (the member of 
this stain combination which stains the mitochondria). Further, 
in practically all tissue-smear preparations, the ruptured cyto- 
plasm is distinctly stained by the pyronin. This latter action 
of the stain is interesting on account of the supposition (original 
contention of Pappenheim?) that pyronin-methyl green is a 
selective stain for certain lymphocytes, staining their cytoplasm 
pink or red. 
It appears reasonable to the author that in the cases where the 
cytoplasm stains with the pyronin the mitochondrial substance 
has diffused into the cytoplasm. If this interpretation is correct, 
it assumes that mitochondria are composed of a substance that 
is miscible with cytoplasm. It, further, assumes that under 
normal conditions mitochondria have a wall, pellicle, outer 
membrane, or some limiting structure. The diffuse character 
of the mitochondrial substance has also been observed in 
the ordinary fixed and stained mitochondrial preparations of 
lymph nodes. 2 
