390 Prof. Christison on the Poisonous Properties of Hemlock, 



Nor does he seem to me to have correctly interpreted the pheno- 

 mena, since he describes the animals as having been affected with 

 paralysis and tetanic convulsions, and as presenting, immediate- 

 ly after death, congestion and loss of irritability of the heart, with 

 unimpaired irritability of the voluntary muscles, the diaphragm, 

 and the intestinal canal. The natural inference would be that 

 conia proves fatal by paralyzing the heart. 



On making trial of its effects on one of the higher orders of 

 animals, I obtained results so different and so remarkable, that I 

 was led to investigate its physiological action in detail. The facts 

 thus brought under my notice will shew that this substance is one 

 of the most extraordinary of all known poisons, looking either to 

 its uncommon energy and subtilty, or to the peculiar phenomena 

 and nature of its operation. In what follows I shall confine my- 

 self to a general summary, reserving the details of special experi- 

 ments for an appendix. 



I should premise that the anatomical details were conducted 

 by Dr Sharpey, and the whole experiments made in presence of 

 various practised observers. This it is material to state, because 

 in physiological inquiries like the present, where the incidents 

 succeed one another with extreme swiftness, it is indispensable 

 that the anatomical part be executed with facility, certainty, and 

 despatch, and that the account taken of what passes be checked 

 by several competent observers. 



Conia is probably a deadly poison to every order of animals. 

 It acts at least with great, and apparently equal energy on the 

 dog, cat, rabbit, mouse, kite,* pigeon,* sparrow,* frog, slow- worm,* 

 earth-worm,* fly, and flea. 



It acts through every texture of the body where absorption is 

 carried on readily, namely, when put into the stomach, or dropped 

 into the eye, or inhaled into the lungs, or introduced into the cel- 

 lular tissue under the skin, or brought in contact with the peri- 



* Animals experimented on by Geiger. 



