FiTCHETT. — Physiological Action of Tutin. 303 



no symptoms, was quite well the next day, and continued well. Apparently 

 unchanged seeds were recovered from the faeces. 



An attempt was made to induce a domestic fowl to eat some of the fresh 

 fruit (Exp. 32). After being deprived of food for two full days, it was 

 offered a heaped plateful (5 oz.) of berries. After eating about 1 oz, to 1^ oz. 

 it desisted, and ate no more, although it had no other food given it for two 

 days longer. It displayed no symptoms. 



The immunity of birds from poisoning by the seeds under natural con- 

 ditions may be explained perhaps by — (1) The large number of seeds that 

 must be ingested in order .to provide a lethal dose ; (2) the seeds being small 

 and hard, and probably passing through the animal unchanged, as was noted 

 to be the case in Exp. 31. Their relative immunity may possibly be ac- 

 counted for in some measure by — (1) The higher rate of oxidation ; (2) the 

 fact that the kidneys in birds are able to secrete substances in a semi-solid 

 condition, certain normal constituents of the urine — urates and uric acid — 

 having been observed by Bowman (25) in the cells of the tubules. This would 

 suggest that the excretory power of the tubule cell for insoluble substances is 

 greater in birds than in mammals. If this suggestion be applied to the case 

 of a poison that is with difficulty soluble in water circulating in the blood, it 

 may be conceived that this special power of the tubule cell in birds will 

 allow of a more rapid elimination of the toxic body, and so confer a relative 

 immunity. This, of course, applies where the poison is gradually received 

 into the blood, as when absorbed from the alimentary tract. Where, on 

 the other hand, the toxic body is rapidly introduced into the blood, as when 

 given hypodermically, the cells of the tubules have not an opportunity 

 of exercising their special power, and so the relative immunity is not so 

 marked, or does not obtain. This may be illustrated by Exp. 53, where a 

 dose of 5 mlgm. per kilo was given hypodermically to a pigeon weighing 

 335 grams, with the result that convulsions appeared in twenty minutes, 

 and continued without intermission till death occuiTed, forty-two minutes 

 after the injection. 



The question of the relation of the Hver to a glucoside like tutin is an 

 interesting one, and especially so in this connection. In birds the veins from 

 the crop are branches of the jugulars, and therefore a toxic body absorbed 

 from the crop, as must have been the case in the experiments cited, enters 

 the circulation direct. In mammals, on the other hand, the gastric vein 

 discharges the blood from the stomach — which, so far as the absorption of 

 poisons is concerned, corresponds to the avian crop — into the portal vein, 

 and therefore the toxic body must pass through the liver before it enters 

 the general circulation. Has the liver-substance any power to increase 

 or decrease the toxicity of tutin ? To determine this, experiments were 

 made on fish. The result was doubtful, but the indications are that the liver- 

 substance does increase the toxic power, possibly by separating the glucose 

 part of the compound from the poisonous part, and so freeing the latter of 

 an innocuous encumbrance. 



Symptoms in Birds. — With a massive dose the animal is almost immedi- 

 ately, with hardly any premonitory symptoms, seized with general convul- 

 sions. The wings are rigidly extended to the full, and are flapped violently. 

 The head is retracted till it lies firmly pressed against the back between 

 the wings, and the bird is thrown over backwards. It turns over and over, 

 and flops about in every direction until exhausted. This period of violent 

 movement does not last more than a few minutes. A final somersault lands 

 the bird on its back, and it lies, with its head drawn back beneath its body, 



