580 



SCIENCE 



[N. S. Vol. XLni. No. 1112 



can be put in the logarithmic form 



u log X + V log 2/ = log z, 



and charted immediately. 



It is even possible to combine two or more 

 charts of the general type we have considered, 

 enabling us to solve equations containing four 

 or more terms. The method is thus almost 

 one capable of handling algebraic equations 

 in general; but further development of the 

 subject would be out of place here. 



Horace G. DEMOfa 



TJNIVEBSITT OF THE PHILIPPINES, 



Manila, P. I. 



THE COORDINATION OF CHROMATOPHORES 

 BY HORMONES! 



The melanophores of the horned toad, 

 Phrynosoma cornutum Harlan, become con- 

 tracted during states of nervous excitement. 

 All attempts to prevent this reaction locally by 

 cutting various nerves have failed. It is thus 

 suggested that the melanophores may be co- 

 ordinated, in part, by a hormone produced dur- 

 ing nervous excitation and carried to all parts 

 of the skin by the circulation. 



The skin of one leg may be isolated from 

 the general circulation, without blocking its 

 nerve supply, by tying a ligature snugly about 

 the leg. When this is done the melanophores 

 of the isolated leg remain expanded after the 

 animal is thrown into a state of nervous excite- 

 ment. The leg appears much darker than its 

 mate. Upon removing the ligature the mela- 

 nophores contract and the leg becomes pale. 

 The effect is not due to a shortage of oxygen 

 or the accumulation of metabolic products in 

 the leg, for such effects do not influence the 

 melanophores of a ligatured leg until much 

 later and then they produce a contraction of 

 the pigment cells. If blood drawn from a 

 horned toad which is in a state of nervous 

 excitement is injected into one of the sub- 

 cutaneous lymph-spaces of a second animal, 

 the skin above the lymph-space will become 



1 Contributions from the Zoological Ijaboratory 

 of the Museum of Comparative Zoology at Har- 

 vard College, No. 273. 



very much paler than that of the rest of the 

 body. The injection of blood from a horned 

 toad which has not been thrown into a state of 

 nervous excitement does not have this effect. 

 During states of nervous excitement the blood 

 contains a substance which causes the pigment 

 cells to contract. 



What is this substance and where is it pro- 

 duced? The conception of a hormone coordi- 

 nating melanophore activity is not altogether 

 novel, for Fuchs (1914, pp. 1546-1547, 1651- 

 1652) has attempted to explain the behavior of 

 pigment cells in amphibian larvse and reptiles 

 by assuming that substances, perhaps internal 

 secretions, which contract the melanophores, 

 are produced in the body under the regulation 

 of the pineal organ. Laurens (1916) has re- 

 cently shown this hypothesis to be inapplicable 

 to the phenomena observed by him in Ambly- 

 stoma punctatum. That the pineal organ is 

 not concerned, primarily at least, in the re- 

 action in the horned toad is proved by the fact 

 that removal of the entire brain anterior to 

 the cerebellum does not prevent the melano- 

 phores from contracting during states of nerv- 

 ous excitation. 



The studies of Cannon and his collaboratorp 

 upon the physiology of the major emotions 

 present a more promising clue to the nature 

 of this hormone. Cannon and de la Paz (1911) 

 have shown that during states of emotional 

 excitement the adrenal glands are activated 

 to such an extent that an increase in the 

 adrenin content of the blood from the adrenal 

 vein may be detected. Spaeth (1916) has 

 amassed a formidable array of facts to prove 

 that the melanophore is " a disguised type of 

 smooth muscle cell." If Spaeth's contention 

 be accepted, it would appear most probable 

 that the melanophores should be controlled by 

 adrenin, which occupies a particularly signif- 

 icant position in the physiology of smooth 

 muscle (compare EUiott, 1905). 



Adrenin has been shown to produce a con- 

 traction of the melanophores of the frog (Lie- 

 ben, 1906) and of Fundulus (Spaeth, 1916). 

 Very minute quantities have this effect upon 

 the melanophores of the horned toad. Ee- 

 moval of the adrenal glands does not prevent 



