in the process of Respiration. 55 



tened cyanide of mercury is exposed to the action of chlorine gas, 

 cyanide of chlorine is formed and bichloride of mercury is thrown 

 down. Reasoning analogically, similar phenomena would be presen- 

 ted by passing chlorine gas through a solution of cyanide of iron ; 

 the compound of chlorine and cyanogen would be formed, and the 

 iron would be rendered evident to the liquid tests in the form of the 

 peroxide. 



These are the principal arguments which I have at present to of- 

 fer in favor of the opinion which has been advanced. If it be asked 

 why it has not been submitted to the test of experiment, my answer 

 is that there is greater difficulty in doing so than may at first sight ap- 

 pear. Supposing it previously proved that cyanide of iron or the hy- 

 drocyanate of iron exists in the blood, what process would be adop- 

 ted for separating the cyanogen from its combination ? If in the state 

 of a hydrocyanate, we might by passing through it a stream of car- 

 bonic acid, separate the hydrocyanic acid, but even this would re- 

 quire the application of heat ; and moreover, hydrocyanic acid is ve- 

 ry liable to spontaneous decomposition and is resolved into its ele- 

 ments. Or supposing the actual existence of cyanide of iron, we 

 should probably be able to decompose it by a stream of sulphuretted 

 hydrogen, which would afford hydrocyanic acid and sulphuret of iron ; 

 but in this case also the expulsion of the acid would require heat. 

 In either of these methods, therefore, though as might be inferred 

 from what is already known, we should be successful, the formation 

 of hydrocyanic acid, might be ascribed to the heat employed in the 

 processes. 



There is one method, however, which appears to me destitute of 

 objection on this score. And it is to submit a portion of blood to 

 the action of chlorine gas, for the purpose of ascertaining whether cy- 

 anide of chlorine can be formed in this manner. If successful, it 

 would, taken in conjunction, with the known effect of chlorine upon 

 blood, (viz. that of rendering the iron manifest by the ordinary tests) 

 amount to a complete demonstration of the presence of cyanide of 

 ron. But this process is tedious and difficult, and I must leave it 

 to those who are better acquainted with the nature of this singular 

 compound, and who possess better advantages for pursuing research- 

 es of this kind. 



I cannot refrain from applying the above view of the constitution 

 of the blood, to the explanation of the production of Animal Heat. 



