136 PHYSIOLOGY OF THE IXVERTEBRATA. 



chanares to a brown colour in contact with air. But the 

 coagulum produced by alcoliol is not acted upon by air. 



When the oxidised or brown blood is examined by the 

 spectroscope, it does not show any characteristic absorption 

 bands. 



At first sight the blood of Orijctcs appears to contain a 

 substance acting under the influence of oxygen in a similar 

 manner to ha3moglobin or htemocyanin. The substance 

 which becomes brown in air, does not probably play any rule 

 in the respiration of the animal. The blood in the vessels is 

 perfectly colourless ; the brown colour which is produced 

 after it has been extracted from the body is probably a 

 cadaveric or post mortem phenomenon comparable to the 

 spontaneous coagulation which equally occurs in this liquid. 

 In fact, the colourless substance, which becomes brown on 

 exposure to air is not contained in the blood which circulates, 

 but is formed at the moment of spontaneous coagulation. If 

 one carefully plunges the larva3 of Oryetcs into warm water 

 (50° to 55° C.) for a quarter of an hour before opening it, 

 the blood extracted from the dorsal vessel neither coagulates 

 nor colours in air. 



The production of the colourless substance (susceptible of 

 becoming brown in contact with air) has probably been 

 prevented by the temperature of 50' to 55° C. For when once 

 this substance has been produced, the temjoerature of boiling 

 is incapable of preventing its combination with oxygen, and 

 a change of colour which it indicates. 



Finally, the most important fact which proves that the 

 phenomenon of colouration does not play any role in the 

 respiration of the animal, is that the brown substance once 

 formed constitutes a stable combination, which is not decom- 

 posed by acids or alkalies, and is not decolourised when 

 placed in vacuo or in a sealed tube. 



The phenomenon of colouration which the blood of the 

 larvae of Orydes presents when it is exjDosed to air, appears 

 to be a cadaveric phenomenon, and as already stated, com- 



