RESPIRATION 83 



body fluid of Aplysia (Bottazzi) contains less than o"oi per cent, 

 of protein nitrogen. The isoelectric point of haemocyanin is 

 well below absolute neutrality, being according to Quagli- 

 ariello about pH. 47, so that in the slightly alkaline blood of the 

 invertebrates which possess it, it should be dissociated as an 

 anion ; and Quagliariello finds, as might be expected on the 

 assumption that proteins are amphoteric electrolytes, that the 

 acid-neutralising power of invertebrate blood is roughly pro- 

 portional to its protein content. Thus it would appear that 

 the proteins of the blood of invertebrates, as in the mammal, 

 exist normally as sodium salts capable of giving up their 

 kation for the carriage of carbon dioxide away from the tissues 

 as sodium bicarbonate, and that the steep initial portion of 

 the carbon dioxide dissociation curve exhibited by those 

 forms which possess haemocyanin is due to the competition 

 of CO2 and protein anions for the alkali kations of the blood. 



Further Reading 



Books, 

 Barcroft's Respiratory Function of the Blood. 

 Krogh's Respiratory Exchange of Animals and Man. 

 Haldane's Organism and Environment. 

 Haldane's Respiration. 



On Respiration in Cephalopods. 



Polimanti (19 1 2). Beitrage zur physiologic von Sepia II. Arch. f. anat. 



u. Physiol, p. 53 (1909)- 

 WiNTERSTEiN. Zur kenntnis der Blutgase wirbellose Seetiere. Biochem. 



Zeitschr. 19. 



Annelids. 



BoiTNHiGL (1902). Recherches sur la respiration des annelides. Ann. de 

 sci. nat. i6. 



Insects. 



BuDDENBROCK AND RoHR (1922). Die Atmung von Dixipus morosus. 



Zeit. Allg. Physiol. 20. 

 Krogh (1913-20). On the Composition of the Air in the Trachea System. 



Skand. Arch. Physiol. 29. 

 Studien ueber Tracheen Respiration II-III. Pflugers Arch. 179. 



Lee (1924). On the Mechanism of Respiration in Certain Orthoptera. 

 Journ. Exp. Zool. 41. 



