125 



cases, it takes place more slowly than in others. The age of the 

 animal has, in this respect, a most marked retarding influence. On 

 animals only about a third grown, it will often occur at about 2J 

 minutes after immersion, while in the adult it generally requires 

 five minutes and upwards. 



The local effects of immersion are redness, heat, and swelling of 

 the foot, accompanied sometimes with extravasation from some 

 smaller vessels, when the immersion has been prolonged for ten 

 minutes and upward. The sensibility of the part is likewise di- 

 minished, but in no case so as to produce insensibility. The amount 

 of irritation is of course variable, according to the duration of the 

 immersion. It is, however, important to remark that full dilatation 

 of the pupils may be obtained without any symptons beyond those 

 of a temporary active vascularization of the part, which quickly dis- 

 appears when the irritating cause is removed, and which presents no 

 more active symptoms than those produced by neuro-paralysis of the 

 vessels after section of the sciatic nerve. 



If instead of immersing the limb as above, we merely plunge it 

 for a moment in the solution, we likewise may have dilatation of the 

 pupil, but more slowly. 



The same effects are obtained even although the limb be washed 

 on its withdrawal from the solution, which would lead to the inference 

 that the effect in that case is owing to absorption of the atropia, at 

 all events beneath the cuticle. 



In the case of a solution of atropia in turpentine, a still more 

 curious effect is observed, viz. that during immersion in the liquid 

 the pupil scarcely, if at all, dilates ; whereas, immediately after the 

 removal of the limb, the dilatation commences. Dilatation of the 

 pupils will generally persist from twenty-four to thirty-six hours, 

 and the return to the normal size is very gradual. In some cases 

 the pupil may be affected after an immersion of nine minutes, the 

 dilatation reaching three millimetres ; while in others, only a very 

 slight influence is obtained on the pupil after an immersion of from 

 twelve to fifteen minutes. If the limb is then removed from the 

 solution, the pupil dilates to its maximum in a few minutes. After 

 two or three minutes' immersion, the animal shows signs of consider- 

 able pain. Much inflammation of the part follows the action of this 

 solution, which is followed by oedema. 



When we immerse the tail of the animal instead of its foot, 



