108 PRODUCTS OF THE DECOMPOSITION OF HAEMOGLOBIN. [BOOK I. 



which can afterwards be obtained from it by distillation after acidu- 

 lating with sulphuric acid. It is to be noted that the spectrum 

 of the supposed hydrocyanic compound is identical with that of 

 oxy-haemoglobin, and that the behaviour of the solution to reducing 

 agents is absolutely the same as that of a solution of oxy-haemoglobin. 



Those who advocate the existence of the compound however rely 

 somewhat upon the fact that blood to which hydrocyanic acid has been 

 added shews the bands of oxy-haemoglobin, or bands identical with 

 them, for a much longer time than normal blood a fact which 

 they explain by supposing that the hydrocyanic compound is some- 

 what more stable than oxy-haemoglobin. 



It appears to the Author that all proofs of the existence of such 

 a compound are wanting. That some hydrocyanic acid should adhere 

 to the haemoglobin as it crystallizes out is quite in accordance with 

 a variety of experiences of a similar kind, and can by itself afford 

 no evidence of an actual compound existing. The resistance of 

 hydrocyanic blood to decomposition can on the other hand be easily 

 explained by the unquestionable arrest or slowing 'of the process 

 of putrefaction in the presence of hydrocyanic acid ; it is undoubtedly 

 the products of putrefaction which are the causes of the spontaneous 

 reduction of the oxy-haemoglobin of blood confined in a vessel which 

 has no access to air, so that an agent which will inhibit putrefaction 

 and at the same time not decompose oxy-haemoglobin would be 

 expected to act as hydrocyanic acid acts and cause the persistence of 

 the oxy-haemoglobin bands. 



Products of the decomposition of Haemoglobin. 



When subjected to the action of various reagents, especially to that 

 of acids and of salts having an acid reaction, the molecule of haemo- 

 globin undergoes a profound decomposition, the ultimate products of 

 which are, amongst others, a proteid substance or substances, and a 

 body called HAEMATIN, which contains all the iron originally con- 

 tained in the blood-colouring matter. The formation of haematin 

 is, according to Hoppe-Seyler, necessarily dependent upon the 

 presence of oxygen, in the absence of which the process of decom- 

 position yields a proteid and a body to which he has given the name 

 of HAEMOCHROMOGEN ; the latter may by oxidation pass subsequently 

 into haematin. Haematin is an interesting body which forms definite, 

 well crystallized, compounds with hydrochloric, and apparently also 

 with hydriodic acid. 



Before describing the various bodies which are the products of 

 a profoundly decomposing action exerted upon haemoglobin, it is 

 essential to refer to a modification of haemoglobin which is brought 

 about by the action of various agents, and concerning which very 

 much difference of opinion still lingers, viz. methaemoglobin. 



