308 COLOURING MATTERS. 



there is at once an end to all those very imaginative hypotheses 

 which assume that the iron takes a great share in the process of 

 respiration, and that it is the conveyer of oxygen to the blood. 



The experiments of Bruch* on the action of gases on the colour 

 of the blood, and the observations of Harless,f regarding the 

 gradual destruction of the corpuscles of frogs' blood, certainly 

 indicate that there is a chemical action between the blood-corpuscles 

 and their contents on the one hand, and the inspired oxygen on the 

 other, in which action the hsematin doubtless participates. 



The observations of Hannover, t which show that persons whose 

 blood is very deficient in red corpuscles (chlorotic persons) exhale 

 as much carbonic acid as healthy persons, seem on the other hand 

 to contra-indicate a direct relation between the blood-corpuscles or 

 blood-pigment, and oxidation in the blood. We must, therefore, 

 give up for the present all attempts at understanding the function 

 of the blood-pigment. 



The question as to what becomes of the hsematin when the 

 blood-corpuscles and their contents undergo disintegration, is one 

 which for a long time was enshrouded in perfect obscurity, but on 

 which some light has now been thrown by Virchow's admirable 

 investigations on haematoidin. The occurrence, in a crystalline form, 

 of this substance, which is undoubtedly derived from the blood- 

 pigment, and its different behaviour towards the same reagents, 

 indicate that, notwithstanding its crystalline arrangement, it con- 

 tinues to undergo changes which give rise to a substance perfectly 

 similar to, if not identical with, bile-pigment or melanin. Although 

 the subject is still far from being satisfactorily settled, Virchow was 

 the first who by his pathologico-histological and chemical investiga- 

 tions prominently brought forward definite facts which have afforded 

 the first solid groundwork for the hypothesis which was long since 

 propounded, that hsematin might be transformed into cholepyrrhin. 



In reference to this point we would specially direct attention to 

 Virchow's ingenious treatise, in which he endeavours to strengthen 

 the view regarding this metamorphosis by means of a simple induc- 

 tion based on direct observation. It has unfortunately hitherto 

 been found impossible to separate hsematoidin in so pure a state 

 and in sufficient quantities as to admit of its being subjected to a 



* Zeitschr. f. rat. Med. Bd. 3, S. 300, 



t Ueber den Einfluss der Gase auf die Blutkorperchen von Rana tonipor. 

 Krlangen, 1846. 



$ De quantitate acidi carbonic! ab homine sano et aogroto exlialati. 



I84a. 



