242 Scientific Proceedings (115). 



It was found that the toxicity of the drugs varied with the 

 age of the tadpoles and with the nature of the drug. Very young 

 tadpoles succumbed much more quickly to all the poisons than 

 the older ones when placed in solutions of the drugs of the same 

 concentration. Tadpoles 1 and 2 days old quickly died in all 

 the solutions unless the drugs were present in a very dilute con- 

 centration. Older tadpoles continued to live in solutions of all 

 the drugs longer than was at first expected. The most toxic of 

 the 3 drugs in point of dosage was nicotine. Next in toxicity 

 came caffeine and the weakest of the 3 drugs studied was ethanol. 

 It was surprising to find that while caffeine even in great dilution 

 prqved deleterious to the growth and development of the tad- 

 poles, ethanol affected the animals to a much lesser degree. 

 Thus it was found that while tadpoles of the age of 8 days when 

 placed in a solution of nicotine, 1-50,000 succumbed on the 23d 

 day, other tadpoles of the same age placed in caffeine solution, 

 1-10,000 died on the 12th day, while still other tadpoles of the 

 same age placed in a solution of ethanol, 1-100, by volume, lived 

 as long as 40 days. It was furthermore noted that tadpoles 

 placed in solutions of ethanol, 1-500, lived even longer and ap- 

 peared to be but slightly affected by the drug. Further experi- 

 ments on the subject are in progress. This investigation was be- 

 gun in the spring of 1920. 



121 (1703) 



The nutritive properties of milk with special reference to growth 

 and reproduction in the white mouse. 



By H. A. MATTILL. 



[From the Department of Physiology, University of Rochester, 

 Rochester, N. Y.] 



In a recent paper 1 from this laboratory some success was re- 

 ported in correcting the failure of rats to reproduce by the addi- 

 tion of yeast to a ration of powdered whole milk. The value of 

 yeast had been indicated by some simultaneous experiments on 

 the white mouse. As was suggested by Miss Wheeler some years 

 ago, 2 the mouse, unlike the rat, cannot grow normally on an ex- 



1 Mattill, H. A. and Conklin, R. E., /. Biol. Chem., 1920, xliv, 137- 



2 Wheeler, Ruth, J. Exp. Zool., 1913, xv, 209. 



