296 THE BEHAVIOUR OF HYLA AUREA TO STRYCHNINE, 



Although there are considerable variations, as will be noted 

 later, the minimal lethal dose of strychnine for Hyla is to be 

 expressed in terms of milligrams per gram of body-weight or 

 grams per kilogram of body-weight. The increased resistance to 

 strychnine of Hyla over Rana is therefore very considerable. Of 

 the 108 frogs injected, 48 received doses of less than 1 mg. per 

 gm. body-weight. Five died and forty-three recovered. The five 

 which died received 002, 0-02, 0-08, 009, and 009 mg. per gm. 

 respectively. The remaining 60 frogs received doses of 0*1 gm. 

 per gm. or greater doses. Forty-six died and fourteen recovered. 

 The frogs which survived may be classified as follows — three 

 received 0*1 mg. per gm., two received 0*11 mg. per gm., two 

 received 0*12 mg. per gm., one received 0*13 mg. per gm., two 

 received 0*14 mg. per gm., and four received more than 0*15 mg. 

 per gm. body weight. 



If we adopt the principles set forth by Falck,* we shall deter- 

 mine the minimal lethal dose by adopting the dose at which an 

 equal number of frogs died and recovered. It is found that this 

 dose lies between 0*09 and 0-10 mg. per gm. body-weight. 

 Table ii. gives a record of the number of frogs injected with each 

 dose, the number which died, and the number which recovered. 



During a number of the experiments the sex of each frog was 

 noted. It was thought that as the female frogs weighed heavier 

 than the male frogs owing to the large ovaries, some variation in 

 the toxicity might be observed. No differences were, however, 

 demonstrated in the effects of the doses of strychnine employed. 



The difference! in the behaviour of frogs collected in summer 

 (December) and those collected in winter (June) was, however, 

 somewhat marked. 



* Loc. cit. 

 + See Chapman, Proc. Linn. Soc. New South Wales, xxxi. p.362, 1906. 



