138 BOARD OF AGRICULTURE. 



and beautiful absorption bands were observed in the spectrum 

 when light was passed through the blood, before being examined 

 by a prism ; and Prof. Stokes ascertained that the blood-coloring 

 matter is capable of existing in two conditions, in one of which 

 it is more highly oxidized than the other ; that the less oxidized 

 substance may be readily produced by acting upon blood by 

 suitable reducing solutions ; that it is characterized by a single 

 and very characteristic absorption band, and that by mere agi- 

 tation with air it again becomes converted into the more highly 

 oxidized substance. 



Independently of each other, my brother * and Hoppe Seyler 

 discovered that blood which has been treated with carbonic 

 oxide, besides acquiring a permanently florid character, remains 

 quite unaffected by such reducing agents as were shown by 

 Stokes readily to deoxidize blood-coloring matter ; i. e., the 

 two bands of scarlet cruorine remain unchanged, and are not 

 replaced by the wide absorption band of reduced or purple 

 cruorine. My brother considers that the florid color of blood 

 treated with carbonic oxide is due to a decided action on the 

 constituents of the red blood corpuscles, which Bernard showed 

 retained their shape under sucli circumstances for a remarkable 

 length of time. " When blood saturated with carbonic oxide is 

 placed for -a considerable time in the vacuum of a good air- 

 pump, and the exhaustion is pushed till the tension of the air 

 in the receiver does not exceed three or four millimetres, no 

 change is produced in the properties of the blood. After the 

 exposure in vacuo the blood is still irreducible." 



" When such blood is evaporated to dryness in the water-bath, 

 at a heat not exceedhig 140° Fahr., the dry residue, when treated 

 with water, yields a solution of coloring matter which is as irre- 

 ducible as the original blood." 



" When a solution of blood is mixed with a very large excess 

 of a reducing solution, and carbonic oxide is then passed into 

 the solution, at once the single band of reduced cruorine disap- 

 pears, and gives place to the two well-marked absorption bands 

 characteristic of scarlet cruorine and carbonic oxide cruorine." 



* For my brother's observations and researches, see the article from 

 wliich I am quoting, entitled " On Poisoning by Carbonic Oxide Gas and 

 Charcoal Fumes ; " Journal of Anatomy and Physiology, No. II., published 

 by Macmillan & Co., Cambridge. 



