PHYSIOLOGY, CHEMISTRY AND PATHOLOGY 15 



tory. Immediately after hatching, and before the oral orifice had opened, 

 they were grouped in trays into colonies of 200, arid food was placed in 

 the trays. The food was weighed, each colony receiving the same amount 

 triweekly. All foods were taken voraciously by the tadpoles. By means 

 of a water dropping and disposal system, the tadpoles were kept at all 

 times in fresh, aerated tap water. Moreover, the trays were frequently 

 shifted to average environmental conditions of light and temperature. In 

 the observations on pigmentation, some 12,000 tadpoles were used. 



The food consisted of desiccated glandular material and fresh plant 

 food. Of the glands, the effects of pineal (adult and preadult), thyroid, 

 parathyroid, and suprarenal were tested. Brain tissue and beef muscle 

 were used as controls. Different lots of tadpoles were fed upon Spirogyra, 

 bread crumbs and hemp seed as a further check. A single lot of tadpoles 

 was fed on desiccated retinae from beef eyes as a particular experiment. 

 Of these tissues the pineal gland alone produced the phenomenon charac- 

 terized as the pineal pigment cycle. 



After the tenth day of larval life, pigment changes were always evi- 

 dent after every feeding of the pineal tissues, and the animals continued 

 to react until the age when their forelegs protruded. Sufficient blanching 

 of the bodies occurred, within thirty minutes after pineal feedings, to dif- 

 ferentiate these colonies from their controls. A maximum condition of 

 translucency was attained in about forty-five minutes, and three to six 

 hours later restoration of the original color was complete. The difference 

 was first noticeable in the region about the eyes, due to the absence of 

 larger viscera. It can be demonstrated, however, that the reaction occurs 

 simultaneously over the whole body. At the height of the reaction, the 

 integument was so transparent that the brain, the olfactory tracts, the 

 kidneys, the beating heart, and the intestines were all clearly visible 

 through the dorsal body wall. 



Figures 2 and 3 are drawings of a single tadpole, just prior to, and 

 forty-five minutes after feeding pineal material. The darker portions in 

 3 are due to the denser viscera, the pigment conditions being the same 

 over the entire animal. 



These described alterations in pigmentation are invariably induced in 

 tadpoles upon the administration of pineal materials, be they the fresh 

 minced glands, simple desiccation preparations, simple aqueous extracts, 

 or certain lipoderivatives of the glands. 



This pineal depigmentation was shown to be due to the clumping into 

 small spheres of the pigment granules which under normal conditions are 

 evenly distributed throughout the melanophores. 



Feeding Experiments in Human Subjects. Following the establish- 

 ment that pineal extracts when fed to animal subjects stimulate an in- 

 creased cellular activity, there arose the high hope that this substance 

 might prove efficacious in activating the undeveloped, dormant cells in 



