1896.] On Turacin and Turacoporpliyrin in the Blood. 339 



value, a shower of fine rain falls, and this settles within a very few 

 seconds ; if, however, the same expansion be made while the air is 

 exposed to the action of the rays, or immediately after, the drops are 

 sufficiently numerous to form a fog, which persists for some minutes. 



In order that direct electrical action might be excluded, experi- 

 ments were made with the vessel containing the air wrapped in tin- 

 foil connected to earth. This was exposed to the rays ; the air was 

 then expanded, the current switched off from the induction coil, and 

 finally the tinfoil removed to examine the cloud formed. 



As before, a persistent fog was produced with an expansion which 

 without the rays would only have formed a comparatively small 

 number of drops. 



It seems legitimate to conclude that when the Rontgen rays pass 

 through moist air they produce a supply of nuclei of the same kind 

 as those which are always present in small numbers, or at any rate of 

 exactly equal efficiency in promoting condensation. 



VII. " On the Relations of Turacin and Turacoporphyrin to the 

 Colouring Matter of the Blood." By Arthur Gamgee, 

 M.D., F.R.S., Emeritus Professor of Physiology in the 

 Owens College, Victoria University. Received March 12, 

 1896. 



In a recent paper read before the Royal Society, I have shown that 

 the intense absorption band in the extreme violet, which is observed, 

 by means of photography, in the spectrum of highly diluted solutions 

 of haemoglobin and its compounds, is (with slight changes in its 

 position) exhibited by certain of the derivatives of the blood colouring 

 matter, e.g., by haBmochromogen and the compounds of haamatin, and 

 by that remarkably interesting coloured but iron-free derivative of 

 the latter body, haamatoporphyrin. 



Having found that no organic body which I had examined (not 

 even such as the colouring matters of aTkanet-root or picro-carmine, 

 which present in the visible spectrum absorption bands not unlike 

 those of the blood colouring matter) exhibits an absorption band 

 occupying the position, or possessed of the remarkable intensity, of 

 the extreme violet band under discussion, it seemed as if the latter 

 owed its origin to a group of atoms existing in and perhaps charac- 

 teristic of the blood colouring matter, which group remains intact 

 in certain of the products of decomposition of the complex haemo- 

 globin molecule, whereas it does not exist in certain other of the 

 derivatives of the haBmochromogen or haBmatin moiety of the molecule, 

 such as bilirubin and urobilin. 



