MELANOPHORES OF THE HORNED TOAD 303 



the melanophore pigment at this time, one might expect to find 

 the pigment contracted under other conditions which are known 

 to activate the adrenal glands. 



Cannon and Hoskins ('11) found that during asphyxiation the 

 adrenal glands of the cat are activated. Itami ('12) suggests that 

 the effect of carbon dioxide upon the vascular system is probably 

 due in part to an increased secretion of adrenin. If horned toads 

 are placed in a glass vessel through which carbon dioxide is 

 passed, the skin becomes very pale in ten minutes. At this time 

 the animals have become lethargic, but are still able to recover 

 from the treatment. 



Etherization decreases the residual adrenin in the cat's adrenal 

 glands about 50 per cent, according to Elliott ('12) . The melano- 

 phores of horned toads almost invariably exhibit a contraction of 

 their pigment when the animals are etherized. 



Morphia has been shown by Elliott ('12) to cause exhaustion of 

 the adrenal glands. If 0.1 cc. of a 10 per cent solution of morphia 

 oleate is injected under the skin of a horned toad, the pigment be- 

 comes contracted completely within a few minutes. 



Nicotine has an effect upon the adrenal glands similar to that 

 of morphia (Cannon, Aub and Binger, '16). Injection of nicotine 

 also produces a contraction of the melanophore pigment of the 

 horned toad. This effect is due in part to the direct action of this 

 drug upon the pigment cell, for if nicotine is injected into a leg 

 about which a ligature is firmly tied, this leg alone will become 

 pale. 



It is quite possible that the effects of asphyxiation, etherization, 

 and morphia are also due to a direct action upon the pigment 

 cells. At least it can be said that there is no contradiction 

 between the observed behavior of the pigment cells and the 

 behavior to be expected if they are affected by the secretion of 

 the adrenal glands. The melanophore pigment of the horned 

 toad is contracted during nervous excitement, asphyxia, ether 

 anaesthesia, and poisoning by morphia and nicotine— conditions 

 which are known to produce activity of the adrenal glands in 

 mammals. 



