PHYSIOLOGY, CHEMISTEY AND PATHOLOGY 29 



extracts. In the case of pituitary and adrenal extracts, elaborate and 

 reasonably precise methods have been evolved for determining in terms of 

 physiologic activity, the relative strength of various preparations. These 

 quantitative standardization methods have been of immeasurable value 

 for pituitary extracts for which no specific chemical tests have been devised, 

 either qualitative or quantitative. The lack of similar tests for determin- 

 ing the strength of pineal extracts has hampered investigations directed 

 toward ascertaining whether active principles of the pineal are confined to 

 the glands of preadult animals, and whether heating and various forms of 

 chemical manipulation destroy these principles. In fact, in case of any 

 attempts at concentration and purification of pineal extracts involving 

 fraetioning, no means are accessible to indicate which fraction retains the 

 active substances. 



Technic. The only attempt to quantitatively measure the strength of 

 extracts from this gland has been made by McCord and Allen (a) in 1916. 

 These writers point out that the action of pineal materials on pigmenta- 

 tion in tadpoles is a quantitative phenomenon which may be used as the 

 basis for strength computation. In the feeding of pineal materials to 

 the tadpoles, the time interval necessary to establish maximum contrac- 

 tion of the pigment cells increased as the concentration decreased. Tad- 

 poles placed in a 1 :500 pineal emulsion were noticeably lighter in five 

 minutes, and required but thirty minutes to arrive at maximum trans- 

 lucency. In higher dilutions the maximum translucency was attained 

 only after a longer interval and in very high dilutions producing only 

 qualitative changes, the maximum was not attained. The dilution of 

 1:100,000 was the highest that produced a microscopically discernible 

 qualitative action. 



The quantitative relations between concentration and time will be evi- 

 dent from the following table : 



The maximum reaction was determined by comparison with a stand- 

 ard, consisting of several tadpoles which had been placed in a 1 :500 pineal 

 emulsion thirty minutes prior to the beginning of the experiment. The 

 translucency thus obtained was found to be maximum. It served as the 



