The Functions of the Blood. 89 



found that a solution of the blood-corpuscles/ from arterial 

 blood — a solution, that is, consisting mainly of scarlet cruorine — 

 when excluded from the air, slowly reduced itself, and showed, 

 after a time, the purple colour and the one-line spectrum of 

 purple cruorine. On opening the tube and shaking it with air 

 the scarlet colour returned, and with it the two-line spectrum. 

 Hence it is clear that scarlet cruorine is capable of oxidizing a 

 portion either of its own substance or else of the serum, from 

 which it is impossible wholly to free it in the experiment. 

 Whichever it be, it certainly is a part of the blood itself which 

 is oxidized by the cruorine ; and this fact is, as we shall pre- 

 sently see, in perfect accord with the theory to which we are 

 led by other considerations. 



These curious optical experiments, apart from their physio- 

 logical interest, have already yielded some practical results of 

 considerable importance. Soon after the publication of Stokes's 

 memoir, Mr. H. 0. Sorby contrived an ingenious adaptation of 

 the spectroscope to the microscope, and by its means suc- 

 ceeded not only in repeating all Stokes's experiments, but also 

 in furnishing medical jurisprudence with a new and most valu- 

 able means of identifying blood-stains. The spectrum-micro- 

 scope has since but somewhat improved in construction, and 

 many readers of this journal have no doubt seen it, and the 

 beautiful experiments which its inventor performs with it at 

 some one of the recent scientific soirees. It is described in 

 detail in a paper by Mr. Sorby, read before the Eoyal Society, 

 April 11, 1867. A scrap of blood-stained fabric, l-10th of an 

 inch square, containing possibly not more than 1-1 000th of 

 a grain of colouring matter, may be experimented upon by its 

 means, and the most certain evidence of the nature of the 

 colour obtained. It has already been found useful in criminal 

 trials. 



Another interesting application of the spectroscopic ex- 

 amination of blood was made by Hoppe-Seyler. Claude 

 Bernard discovered, some years ago, that the poisonous action 

 of carbonic oxide gas was due to the circumstance that it had 

 the power of displacing all the loosely-combined oxygen from 

 the corpuscles, and of occupying its place in a somewhat more 

 stable form of combination. All blood, veinous as well as 

 arterial, after treatment with carbonic oxide, acquires a uniform 

 red tint, which it retains with singular persistency, being, in 

 fact, as Bernard expressed it, mineralized by the gas. Hoppe- 

 Seyler submitted some of the blood so treated to optical ex- 

 amination, and found that it gave a spectrum very similar to, 

 but not identical with, that of scarlet cruorine. But when ex- 

 cluded from the air, instead of reducing itself like scarlet 

 cruorine does, it remained unchanged for an indefinite period 



