ZOOLOGY: A. C. RED FIELD 
205 
ophore pigment is contracted by adrenin may be taken as a strong indi- 
cation that the melanophores are under the control of the sympathetic 
division of the autonomic nervous system (ElHott, 1905).^ A resem- 
blance therefore appears between the mechanism coordinating the 
melanophores of the horned toad and that coordinating the smooth 
muscles of the mammalian body. 
Smooth muscles commonly possess a double innervation, each con-- 
tractile element being influenced by fibers from the sympathetic and 
from the cranial or sacral division of the autonomic nervous system. 
These pairs of fibers act in an opposite sense upon the muscle. Here- 
tofore no analog of the cranial-sacral division has been demonstrated 
to affect melanophores. The melanophores of the Florida chameleon, 
Anolis carolinensis, are controlled by nerves belonging to the autonomic 
nervous system, impulses from which cause their pigment to expand 
(Carlton, 1903).^ If these fibers belong to the sympathetic division 
of the autonomic nervous system, adrenin should have a similar effect 
upon the pigment cells. Adrenin, however, contracts the melanophore 
pigment of AnoHs. It is suggested, consequently, that the melano- 
phores of Anolis are controlled by fibers analogous to the cranial- sacral 
autonomic nervous system of mammals. It is not improbable that 
both divisions of the autonomic nervous system are in control of the 
melanophores of many vertebrates, but only that division manifests 
itself which dominates when the nerve trunks are stimulated. 
The resemblance between the coordinative mechanism of melano- 
phores and smooth muscles supports the contention of Spaeth (1916)^ 
that these pigment cells are functionally modified smooth muscle cells. 
The fact that this mechanism is brought into action during nervous 
excitement indicates that the physiological basis of emotional mani- 
festations is similar in reptiles and mammals. 
^ Contributions from the Zoological Laboratory of the Museum of Comparative Zoology 
at Harvard College. No. 293. 
2 Redfield, A. C, The coordination of chromatophores by hormones, Science, New York, 
N. S., 43, 1916, (580-581). 
3 Elliott, T. R., The action of adrenalin, /. Physiol., London, 32, 1905, (401-467, 2 figs.). 
^ Carlton, F. C, The color changes in the skin of the so-called Florida chameleon, Anolis 
carolinensis Cuv, Proc. Amer. Acad. Arts Sci., Boston, 39, 1903, (257-276, 1 pi.). 
^ Spaeth, R. A., Evidence proving the melanophore to be a disguised type of smooth 
muscle cell, /. Exp. ZooL, Baltimore, 20, (193-215, 2 figs.). 
