Comparative study of ethanol,caffeine and nicotine on the development of frogs' larvæ

The effects of ethanol, caffeine (alkaloid) and nicotine (alkaloid) solutions were studied on the growth and development of the larvæ of two species of frogs, viz., Rana sylvatica and Rana palustris. The study of the larvæ was begun immediately after hatching from the eggs and continued on tadpoles of older ages. Tadpoles of the same species and ages were placed in solutions of the above drugs of various concentrations and the effect of the poisons was noted.

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 concentration. 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 proved deleterious to the growth and development of the tadpoles, 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, I-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.