284 RAMBLES OF A NATURALIST. 



less liquid which was loaded with very minute 

 granules whose movements indicated those of the 

 liquid itself. This characteristic structure was in it- 

 self sufficient to authorise us in regarding these appen- 

 dages as true branchia3, but I wished to obtain a 

 more decisive proof for my own satisfaction and that 

 of others. 



By means of a finely pointed syringe, I injected into 

 the canals which connect these appendages a preci- 

 pitate of iron of a faint bluish colour, which has the 

 property of becoming darker on being brought into 

 contact with oxygen, and of becoming changed into 

 a Prussian blue colour. I took care to select an 

 animal that was full of life and activity, but although 

 the operation was perfectly successful, I did not at 

 first perceive any change ; the colour of the liquid 

 employed being concealed by that of the tissues. 

 But very soon the air in the water which penetrated 

 through the living tissues of the animal, acted upon 

 my precipitate as it would have done upon the blood 

 itself, and yielded to it its oxygen. I saw the 

 appendages become rapidly coloured, whilst the 

 vessels assumed the appearance of undulating lines 

 of a blue tint, which became every moment deeper, 

 and in a very short time I could perceive their rami- 

 fications with a simple lens. This experiment was 

 decisive. I had seen the Branchellion respire the 

 salt of iron, if I may be allowed to use the expres- 

 sion ; the appendages were therefore incontestably 

 branchia3.* 



* In this experiment, the portion of the injected liquid which had 

 penetrated into the interior of the body, did not present any change 



