304 ALFRED C. REDFIELD 



If it could be shown that changes occurred in the histological 

 condition of the adrenal glands of the horned toad or that these 

 bodies become exhausted as the result of any stimulus which will 

 cause a contraction of the pigment, additional evidence that the 

 melanophores are coordinated by the secretion of adrenin would 

 be afforded. It has not been possible to produce any recognizable 

 change in the condition of the glands either by prolonged noxious 

 stimulation or by stimulating the glands directly with an electric 

 current. The method employed, fixing with a mixture of formol 

 and Miiller's fluid, evidently was not suitable for detecting any 

 changes which may occur in the adrenal glands of these lizards. 

 Elhott ('12) was able to demonstrate only a very slight decrease 

 in the residual adrenin after faradizing one of the splanchnic 

 nerves of the cat. 



Although the preceding experiment failed to demonstrate any 

 exhaustion of the adrenal glands, an observation has been made 

 which is significant in this connection. When shipments of 

 horned toads first arrive from Texas the skin of the animals is 

 always very dark in color. If these lizards are subjected to a 

 noxious stimulus, the melanophore pigment becomes contracted 

 only slightly and much more slowly than normally. Some 

 individuals fail to exhibit the reaction at all. Not until after a 

 week does the reaction become normal. When it is remembered 

 that these animals have been crowded together in a small box, 

 and shaken about in an express car for at least five days, it is not 

 surprising that any gland which is brought into activity by 

 nervous excitement should become exhausted. The failure of 

 the reaction in these animals may be explained readily in this way. 

 The bearing of this observation upon the relation of the adrenal 

 glands to the reaction of the melanophores to noxious stimuli will 

 become evident when it is pointed out that Elhott ('12) has 

 found that the adrenin content of the adrenal glands of cats 

 which have been recently brought into the laboratory is below 

 that of animals which have become accustomed to their sur- 

 roundings. 



If the contraction of the melanophore pigment of the horned 

 toad which follows noxious stimulation is due to a secretion of the 



