FUNCTIONS OF BLOOD 



107 



absent from the powerful flight muscles of most birds. The 

 storage function of myoglobin is probably of importance in 

 static contractions when the blood supply becomes inadequate 

 (Lindhard, 1920) and it may also have to function rhythmi- 

 cally in the ordinary process of contraction. 



Ray Lankester (1872) made a very extensive and careful 

 study of the distribution of haemoglobin and found it in many 

 unexpected places. While it is otherwise absent from smooth 

 muscle it is present in the rectal muscles of man and probably 

 other mammals. It is present also in the pharynx and radula 

 muscles of gastropods (observed in Limnaa, Paludina, Littorina, 

 Patella, Chiton, Aplysia) and in the pharyngeal tube of the worm 

 Aphrodite. In all these cases the concentration is rather low, 

 but in the chain of nerve ganglia of Aphrodite it is high enough 

 to give the colour of mammalian blood. About the function 

 in these locations we can only make guesses. 



Fig. 62. Part of the red organ in a young Gastrophilus larva. 



(Prenant.) 



Probablvca. 60 1. 



Certain insect larvae {Gastrophilus) living in the stomach of 

 mammals, especially in the horse, have a peculiar organ made 

 up of large red cells (Fig. 62) which contain haemoglobin in 

 fairly high concentration and are arranged on tracheal 

 branches which supply them with a large number of tra- 

 cheoles. The animal must be exposed to periods of oxygen 

 lack, and there can be no reasonable doubt that the organ 



