204 
ZOOLOGY: A. C. REDFIELD 
THE COORDINATION OF THE MELANOPHORE REACTIONS OF 
THE HORNED TOAD 
By Alfred C. Redfield 
ZOOLOGICAL LABORATORY OF THE MUSEUM OF COMPARATIVE ZOOLOGY, HARVARD COLLEGE^ 
Communicated by G. H. Parker, February 3, 1917 
In a foregoing paper (Redfield, 191 6)^ it was pointed out that the 
melanophores of the horned toad Phrynosoma cornutum are coor- 
dinated by a hormone, produced during nervous excitement, which 
causes its pigment to contract. The following considerations indicate 
that this hormone is adrenin, the secretion of the adrenal glands. (1) 
Adrenin in very minute subcutaneous doses causes a contraction of the 
melanophore pigment. (2) The adrenal glands exhibit the chromaffin 
reaction and their extract not only yields a characteristic physiological 
test for adrenin, but causes the melanophore pigment to contract when 
injected subcutaneously into a horned toad. (3) Faradic stimulation 
of the adrenal glands causes a contraction of the melanophore pigment 
of the skin. (4) The occurrence of "emotional" hyperglucemia in 
the horned toad indicates that adrenin is secreted during nervous excite- 
ment. (5) The melanophore pigment is contracted under conditions 
known to produce adrenal secretion in mammals, i.e., asphyxia, ether 
anaesthesia, morphia and nicotine poisoning. (6) Removal of the ad- 
renal glands blocks the reaction of the melanophores, so that no con- 
traction ,of the pigment accompanies nervous excitement. In the 
majority of individuals it is necessary to destroy the nervous system 
supplying a part of the skin (an operation which of itself does not block 
the melanophore reaction) before this effect of adrenalectomy manifests 
itself. 
The melanophores are also under the direct control of the nervous 
system. Stimulation of the sciatic nerve causes a contraction of the 
melanophore pigment of the leg. Transection of the spinal cord pre- 
vents the melanophores posterior to that region from being affected, 
when, as a result of nervous excitement, the melanophore pigment of 
the remainder of the skin contracts. It is necessary that the adrenal 
glands be removed before this procedure; otherwise the secretion of 
adrenin will cause a contraction of the melanophore pigment of the 
entire body, and thus mask the effect of the operation upon the nervous 
system. 
The nervous system and the adrenal glands act in a supplementary 
way in coordinating the reactions of the melanophores, both being 
called into action during nervous excitement. The fact that the melan- 
