36 HEMOGLOBIN 



and the concentration of the cytochrome which is contained in its 

 substance : 



(1) Bacteria: aerobic bacteria, such as Bacillus subtilis, contain 

 cytochrome or free haematin, while the anaerobic bacteria, B. sporo- 

 genes, are completely devoid of these pigments. 



(2) Yeast. Baker's yeast has a much higher concentration of 

 cytochrome than brewer's yeast. It was proved by Meyerhoff that 

 in presence of glucose, baker's yeast uses ten times more oxygen than 

 brewer's yeast. 



(3) In snails, the greatest amount of cytochrome is found in the 

 active muscles of radula. 



(4) In crabs, the muscles of the body and of the appendages, 

 which contract slowly, contain a small concentration of this pigment 

 which is present in much higher concentration in the active and 

 rhythmically contracting muscles of the heart. 



(5) In frogs, the highest concentration of this pigment is found in 

 the muscles of the heart. 



(6) In birds which fly, the pectoral muscles and the muscles of 

 the heart contain the greatest amount of this pigment. 



(7) In rabbits, the order of concentration is : heart muscles, muscles 

 connected with mastication, diaphragm, muscles of the legs, etc. 



(8) The most interesting examples are, however, found among 

 insects. The high concentration of cytochrome in their wing muscles 

 is undoubtedly connected with the peculiar activity of these muscles, 

 which are capable of producing up to 300 complete contractions per 

 second. On the other hand, the thoracic muscles of wingless insects 

 show only a very low concentration of this pigment. The best example 

 is, however, shown by the winter moth {Cheimatobia brumata): 



The male of this moth which is provided with well developed wings and flies well 

 shows the presence of cytochrome clearly, while the female with reduced non- 

 functional wings scarcely shows the pigment in the muscles. 



Another case is that of the cockroach : 



In cockroaches {Slylopyga orientalis) which do not fly, but are good runners, cyto- 

 chrome is foimd specially in the muscles of the legs. 



The last case has to do with the development of the fly : 



Taking as an example the common blow-fly, we find that cytochrome is already 

 present in the eggs and in the muscles of the larva. The concentration of the pig- 

 ment in these muscles is found to be approximately ten to fifteen times lower than 

 that in the thoracic muscles of the adult fly. During the metamorphosis the concentra- 

 tion of cytochrome in the freshly formed thoracic muscles of the pupa increases with 



