398 



infusion was injected into the rectum of a dog whose head had been 

 cut off, and whose respiration was kept up by artificial means, the 

 heart continued to act in the same manner as in the experiments 

 which Mr. Brodie lately communicated to the Society, without being 

 sensibly affected by the infusion. 



The author's trials of the external application of poisons were con- 

 fined to the essential oil of bitter almonds, the juice of aconite, and 

 the South American poison called Woorara. They all produced the 

 same effects as the two former had done when applied internally, for 

 the heart was observed to contract, as before, long after other sym- 

 ptoms of life had ceased ; so that the circulation could be kept up 

 by means of artificial respiration. 



With respect to the medium through which poisons affect the 

 brain when they are applied to external wounds, the author's expe- 

 riments were confined to the woorara. And he endeavoured to de- 

 termine whether the influence was conveyed by the nerves, or whether 

 the poison itself entered the circulation, either by the absorbents, or 

 through the divided veins. By dividing the nerves of a part, the 

 efficacy of the woorara did not appear diminished, neither did tying 

 up the thoracic duct in any degree interfere with its action. But 

 when a ligature was applied round the leg of a rabbit, so as not to 

 include the sciatic nerve, the rabbit was not in the least affected by 

 the woorara. 



The author consequently infers that the woorara acts upon the 

 brain by passing into its substance through the divided vessels of the 

 part to which it is applied. 



Since the circulation of an animal could be kept up by an artificial 

 respiration, after the brain had been even completely removed, Mr. 

 Brodie conceived it possible that the functions of the brain might be 

 found to recover from temporary suspension if the circulation were 

 continued for a time by artificial respiration, and that thus the life 

 of the animal might be preserved. 



After two experiments, which were not attended with complete 

 success, a third was made upon a rabbit, by applying distilled oil of 

 almonds to a wound in the side. In five minutes it ceased to breathe, 

 and was apparently dead ; but by means of artificial respiration con- 

 tinued for sixteen minutes, it was completely restored to life ; and on 

 the following day appeared not to have suffered from the experiment. 



On the Causes which influence the Direction of the Grotvth of Roots. 

 By Thomas Andrew Knight, Esq. F.R.S. In a Letter to the Right 

 Hon. Sir Joseph Banks, Bart. K.B. P.R.S. Read March 7,1811. 

 [Phil Trans. }8U,p. 209.] 



In a former paper Mr. Knight showed the influence of gravitation 

 on the plumule and radicle of germinating seeds ; in the present he 

 considers the fibrous roots, which, with little comparative regard to 

 gravity, extend themselves in whatever direction the greatest nutri- 

 ment or moisture is to be found, with an appearance of predilection, 



