378 Vlir. HEMATIN ENZYMES, I. CYTOCHROME SYSTEM 



able on the tissues of other vertebrates and none on those of inverte- 

 brates. Table VI summarizes the results of quantitative estimations 

 of cytochrome c obtained by Stotz {267 J^), Potter and Du Bois (2179), 

 and Fujita and co-workers (960). These results are so similar that a 

 compilation in one table is justifiable. 



Heart muscle is usually rich in cytochrome c, but some other red muscles 

 contain even more; Fujita reported very high values for the red muscles of 

 some Japanese fish. White muscles often contain less cytochrome c, but as 

 Hill {1279) has pointed out, the correlation is rather between cytochrome 

 content and rapidity of movement of the muscle than between cytochrome 

 and myoglobin contents. The cytochrome spectrum is particularly strong 

 in the rapidly moving flight muscles of insects. In Australia both drum and 

 flight muscles of the cicadas lend themselves well to a demonstration of the 

 cytochrome system. 



Nerve cells are rich in the cytochrome system (1328,1976,2866), but nerve 

 fibers and central nervous system contain little. No cytochrome spectrum 

 has been observed in the white matter of the brain and no oxidase in the 

 peripheral ganglia, but cerebral cortex and central nuclei contain both (1376). 

 The substantia nigra is particularly rich in oxidase and cytochromes b and c. 

 Adrenal cortex shows the normal cytochrome spectrum; with regard to 

 adrenal medulla the findings are contradictory. Cohen and Elvehjem (459) 

 observed only cytochrome c in the medulla of ox adrenals, while Huszak 

 (1377) reports only cytochrome b. 



Stotz investigated a variety of rat tissues and found a remarkable corre- 

 lation between their content of cytochrome c and of cytochrome oxidase 

 (267 If). Exceptions from this rule have been reported. Early embryos of 

 rats and chicken (2179;267If), some tumors (705, 7 16, 960, 1055, 1327, 1U6, 2 17 8 

 2674.), and also unfertilized sea urchin eggs (cf. below) have been reported 

 to contain oxidase but no cytochrome c. In some instances, however, such 

 disproportion between cytochrome oxidase and cytochrome c has not been 

 found by other investigators. 



In early embryo of rats and chicken cytochrome c is very low (2179,2674) 

 and Stotz has claimed that cytochrome c may be absent in the presence of 

 the oxidase. A comparison of the papers of Albaum and Worley (35) and 

 Yaoi (3148) indicates, however, that both oxidase and cytochrome c appear 

 at the same time in chicken embryos, on about the fourth day. The oxidase 

 content increases rapidly after the eighth day, perhaps more rapidly than the 

 cytochrome c content. 



While cytochrome c was not found spectroscopically in unfertilized eggs 

 of Arbacia or during the diapause of the grasshopper embryo, its presence 

 there appears to be indicated by various facts discussed below. Cytochrome 

 oxidase has been ob.served in bull spermatozoa; cytochrome c had been claimed 

 to be absent, but has now been shown also to be present (Mann, 1864). 

 Arbacia sperm also contains cytochrome c (Ball and Meyerhof, 125). 



The occurrence of cytochrome c and cytochrome oxidase in tumors has 

 been reviewed by Potter (2177). In general, cytochrome oxidase and partic- 



