454 IVAN E. WALLIN 
These illustrations, it seems to me, are sufficient evidence that 
mitochondria may be demonstrated by bacteriological methods. 
In this work various problems in connection with the behavior 
of mitochondria have arisen. ‘These problems have no fundamen- 
tal bearing on the major problem of these studies, and con- 
sequently have not been pursued. 
DISCUSSION 
Aside from the demonstration of staining mitochondria by ’ 
means of bacterial technique, certain facts observed in this study 
are of importance in connection with the main problem. 
In a number of attempts to demonstrate the mitochondria 
in adult dog tissues with the above-described bacteriological 
technique, I have practically failed. Only in a very few instances 
have I been able to distinguish mitochondria-like structure in 
these preparations. These attempts were made with stains from 
a different source than the ones originally used on kitten and 
rabbit tissues. The original were Gribler’s stains. However, 
with the kitten and rabbit tissues the results were not the same for 
all tissues. It was exceedingly difficult to demonstrate any mito- 
chondria-like bodies in the pancreas. I have not been able to 
demonstrate any mitochondria in the salivary glands, thyreoid, 
and suprarenal. On the other hand, it appears quite easy to 
stain the mitochondria in the cells of lymph nodes. It must 
be borne in mind that in all these preparations the tissues were 
crushed when the smear was made. 
Two prominent facts stand out in these results: first, mito- 
chondria are not as delicate as it has been supposed; second, 
mitochondria vary in fragility. 
Regarding the delicacy of mitochondria, Cowdry (718) main- 
tains that the slightest desiccation of a tissue is sufficient to 
alter them. The above-recorded results with bacteriological 
methods demonstrate the fact that mitochondria may retain their 
form and be stained after the degree of desiccation present from 
complete drying in the air. 
These staining reactions, further, indicate the danger in formu- 
lating hypothesis and drawing too extensive conclusions on the 
basis of staining reaction alone. 
