CYTOPLASMIC INCLUSIONS 119 



in mitochondria in the cytoplasm than in mitochondria isolated from the 

 cytoplasm. These observations confirm the validity of the interpretation 

 of mitochondrial reactions in the Protozoa as indicative of a lipoid- 

 protein mixture, but emphasize the need of caution in more specific 

 interpretations before methods as specific as Bensley's are applied to the 

 Protozoa. It is clear that the evidence now available as to the nature of 

 the lipoids and of the proteins in the mitochondria of Protozoa is sig- 

 nificant largely as a lead for further work. 



Horning (1927) adheres to the view that the lipoid component of 

 mitochondria is a phosphatid, but presents no conclusive evidence for 

 this statement. Wermel (1925) found that the mitochondria (or lipo- 

 somes) of Act'mosphaerium react with Ciaccio's method, but according 

 to Lison the only valid interpretation is that unsaturated lipoids are 

 present. MacLennan (1936) stated that the lipoid material in the mito- 

 chondria of Ichthyophthirius is a fatty acid, on the basis of a blue stain 

 with Nile blue sulphate, used according to Lorrain Smith's method. 

 However, since Lison (1936) presents evidence against the specificity 

 of this method, the above interpretation is perhaps too strict, but it is 

 interesting to note that the original interpretation is in accord with 

 Bensley's analysis of the mitochondria of liver. There is likewise a 

 lack of information on the nature of the proteins present. Hayes (1938) 

 demonstrated a positive reaction to fuchsin-sulfurous acid reagent and 

 claimed that nucleic acid is present. However, since lipoids may react 

 in this manner in the "plasmal reaction," it is possible that this test was 

 concerned with the lipoid component rather than the protein portion. 



The metallic impregnation of mitochondria, or the depth of stain taken 

 after the use of lipoid solvents, varies between the species of Protozoa 

 and has usually been considered to be a rough indication of the pro- 

 portion of lipoids present. Thus Scott and Horning (1932) find in 

 Opalina a large amount of lipoid; Lynch (1930) in Lechriopyla, Patten 

 (1932) in Nyctotherus, MacLennan and Murer (1934) in Paramecium, 

 find some lipoid; while Beers (1935) in Didinium finds little if any 

 evidence of lipoids in the mitochondria. Although this data is very 

 crude, foundation is provided for the working hypothesis that there 

 is a wide variation in the probable composition of mitochondria, rang- 

 ing from practically pure lipoid to almost pure protein. Much of this 

 difference represents constant differences between species and could be 



