PHYSIOLOGY, CHEMISTEY AKD PATHOLOGY 13 



0.01 to 0.05 gm. Their results, like those of Hoskins with white rats, 

 were essentially negative. The only variation from the normal, noted 

 either grossly or histologically, was a slight retardation of growth in a few 

 cases. Whether these negative results are to be explained by the fact that 

 the gland material used was previously extricated with ether, remains to 

 be determined. The possibility of such procedure introducing a vitiating 

 factor was earlier mentioned. 



Experiments with Tadpoles. The Influence of Pineal Extracts on 

 Alterations in Pigmentation. The well known color changes in many 

 life forms are obviously in adjustment to environmental conditions. The 

 eye is the essential controlling factor in this adjustment. When in blinded 

 animals certain definite changes in pigmentation still occur, on a priori 

 grounds, it is tenable to assume that the pineal body retains sufficient 

 ocular mechanism to exert its influence upon the pigment cells. This is 

 the hypothesis suggested by Fuchs(fr) in his elaborate monograph on "Der 

 Farbenwechsel und Chromatische Hautfunktion." Many acceptable ob- 

 servations indicate an association between the pineal gland and an earlier 

 optical function. In the reptilian stage of evolution, the pineal as a parie- 

 tal eye probably attained to its highest development. In the embryos of 

 certain lizards (Lacerta agilis), the typical eye structure is still evident, 

 but in no form, living at the present time, does the pineal gland retain an 

 ocular function of high order. Laurens has established experimentally 

 that Fuchs' theory as to the role played by the pineal in pigment changes 

 in relation to the environment is highly improbable. Accepting the con- 

 tentions of Laurens, McCord and Allen reported that although the pineal 

 does not act in the role of its ancient ocular precursor, it contains within 

 itself an active principle capable of inducing pigment changes independent 

 of, and wholly apart from, environmental conditions. The pineal pig- 

 ment changes dominate and appear despite environmental conditions 

 tending toward the opposite phase. 



These workers, in 1915, noted pigmentation alterations in connection 

 with their experiments on the influence of the pineal gland substances upon 

 growth and differentiation processes in tadpoles. On the tenth day of 

 larval life, it was readily observable that in the pineal fed tadpoles the 

 coloration was uniformly lighter than in the control, muscle fed groups. 

 This alteration was at first attributed to some unknown difference in 

 environmental conditions light, background, etc., since the color of these 

 organisms was known to vary considerably in relation to such conditions. 

 These changes when first noticed were trivial in degree, but as development 

 progressed, the alterations in pigmentation became correspondingly greater. 

 Thirty minutes after feeding pineal tissue, the tadpoles which prior to the 

 feeding had been uniformly dark, became so translucent that all the larger 

 viscera were plainly visible through the dorsal body wall. This transluc- 

 ency appeared with such regularity and so punctually after pineal feedings, 



