302 



Transactions. 



Table I. 

 Pigeons. — Minimum Lethal Dose. 



It will be seen that the highest dose recovered from was 10 mlgm. per 

 kilo, and the lowest dose that killed was 10-25 mlgm. per kilo. It may be 

 taken as proved, then, that birds are not really immune, as has been sup- 

 posed, but they are able to withstand a very high dose of the poison by 

 oral administration. 



In noting the current opinion that birds are immune, Easterfield and 

 Aston state (7) that cases have come under their notice in which domestic 

 fowls have been poisoned by eating tutu-berries. This seems barely credible. 

 The lethal dose by the mouth in birds is so high, the percentage of tutin in 

 the seeds so low, the size of the berry in proportion to the size and number 

 of the seeds it contains so great, that it may be doubted if the crop of the 

 ordinary fowl could comfortably accommodate the large number of berries 

 that would be required to provide a lethal dose of tutin. For example, 

 Easterfield and Aston found (7) that the dried seeds of C. ruscifolia contained 

 22-8 per cent, of a green oil, of which 0-18 gram administered to a small 

 kitten produced only very mild symptoms of poisoning. Assuming that this 

 0-18 gram contained 0-0003 gram tutin — a dose which the present writer 

 has found to be feebly toxic to a cat (Exp. -i) — the amount of tutin in the 

 dried seed must be about 0-038 gram in 100 grams. The minimum lethal 

 dose by the mouth in birds is just over 10 mlgm. per kilo, so that in order to 

 get a fatal result, a bird weighing 0-3 kilo (the average weight of a pigeon) 

 would require to eat a little more than 8 grams dried seed, or 150 grams — 

 over 5 oz. — of the fresh fruit. (This statement is based on the relative 

 weights of seeds and berries.) An average-sized domestic fowl would require 

 about 1 lb. of the fruit, and that, of course, assuming that all the tutin would 

 be extracted from all the seeds. To throw light on this point, 5 grams (all 

 that was at hand) of cleaned dried seeds bound with a Uttle moist flour were 

 fed into the crop of a pigeon weighing 314 grams (Exp. 31). It displayed 



