EN THE ANIMAL KINGDOM. 7 



THE DISTRIBUTION OF HEMOCYANIN. 



Hemocyanin is closely allied to hemoglobin, physiologically and chem- 

 ically, but it is farther removed chemically than the histohematins, echino- 

 chrome, chlorocruorins, and the colorless respiratory proteins referred to. It 

 is distributed solely among the invertebrates and, like hemoglobin and 

 the allied bodies mentioned, in an erratic and as yet inexplicable way; 

 but unlike hemoglobin it is found solely in the blood, and as far as known 

 there are no closely related bodies in the form of compounds or deriva- 

 tives, except oxyhemocyanin, that represent or supplement it in various 

 body tissues and fluids. It has the respiratory function of hemoglobin, 

 but chemically it is not nearly so closely related as chlorophyl, as will be 

 seen by the context. Hemocyanin is colorless, and it is the analogue of 

 reduced hemoglobin; while oxyhemocyanin is blue, and is the analogue of 

 oxyhemoglobin, the oxygen being loosely bound as in oxyhemoglobin, but 

 not so readily displaced. 



The blue color of the blood of certain invertebrates was first observed 

 by Ermann, in 1816, in the pulmogasteropod Helix (Abhandl. d. k. Akad. 

 d. Wissensch. z. Berlin, 1819, 199) ; he described it as an opalescence. A 

 few years later Carus (Von d. aussern Lebensbedingungen d. weiss- u. 

 kaltblut. Thiere, Leipzig, 1824, 85) noted the blue color of the bloods of 

 Helix and the crayfish Astacus. Harless and von Bibra (Archiv f. Anat. u. 

 Physiologic, 1847, 148) examined the blue bloods of Eledone, Sepia, Cancer 

 pagurus, and Helix pomatia. They studied the influences of exposure to 

 the atmosphere, O, N, and C0 2 , and they also made elementary analyses. 

 They found that when the colorless blood of Helix was exposed to the air it 

 became blue, and that it became colorless when exposed to an atmosphere 

 of C0 2 ; but they state that the bloods of the cephalopods Eledone and 

 Loligo are affected in the opposite ways by these gases, becoming blue 

 upon exposure to C0 2 and colorless when exposed to O, which, however, 

 has since been shown to be incorrect. Ammonia, they found, removed the 

 blue color, which reappeared upon neutralization with hydrochloric acid. 

 In their analysis of the coloring matter of the blood of Helix they found 



45-79^5. 05^13-23035-93 



and also copper, but no iron. 



Genth (Annalen d. Chemie u. Pharmacie, 1852, LXXXI, 68) found that 

 the blood of Limulus cyclops became blue upon exposure to the air, and 

 that it contained both copper and iron. In his analyses of the ash he found 

 in one case 0.081 per cent of oxide of iron and 0.085 per cent of oxide of 

 copper; and in another only a trace of iron and 0.297 per cent of oxide 

 of copper. 



Haeckel (Archiv f. Anat. u. Physiologic, 1857, 511) observed that the 

 colorless blood of Homola cuvieri upon withdrawal from the animal became 

 gradually gray, and finally an intense blue; and that the bright bluish 

 blood of Homarus became after many hours a dark violet. Witting (Jour, 

 f. pract. Chemie, 1858, LXXIII, 121) refers to the bluish tinge of the blood 

 of Unio pictorum. He also examined the blood of Astacus, but failed to 



