34 



opposite, had he not previously seen Mcyen's statements, to 

 make him cautious. The author has examined, over and over 

 again, a leaf of valisneria prior to its separation from the plant, 

 and has only twice succeeded in finding motion in any of its 

 cells. In these cases, particular care was taken that the speci- 

 mens should not be removed from the field of vision during 

 their excision from the parent stem, and it was found that 

 the circulation was not suspended for an instant. 



"Ordinardy, he has observed, that no circidation in the 

 valisneria is to be found, until the leaf has been separated 

 from the pa/rent at least three minutes; an observation con- 

 firmed by the experience of liis friend Mr. Byerley, of Upton, 

 to whom he has furnished some specimens of the living plant. 



"The author has the same good reason to deny the truth 

 of Meyen's observation on the effects of incision on the chara. 



" If the effects of chemical re-agents upon the circidation 

 are now examined, it is found that there are few which do not 

 put a stop to it more or less completely. 



" A small slip of valisneria, in which regidar and vigorous 

 motions were going on, was placed in contact with a drop of 

 prussic acid (p.l.), in three minutes the motions had become 

 sluggish, and in ten minutes they had ceased in every part. 

 The slip was then removed, and allowed to remain in pure 

 water for about two hours ; at the end of that time the circu- 

 lation was fully established, and, if anything, was more ener- 

 getic than before. This experiment the author has repeated 

 over and over again, and always with the same residt. The 

 prussic 1 acid acts ecpially upon a fresh specimen and one which 

 has been some time cut from the parent; one which has never 

 been touched before, and one which has been often acididated • 

 one which is apparently dead and brown, and one which is 

 still growing and in health. 



" At the suggestion of Dr. Dickinson, the experiment was 

 repeated with the oil of bitter almonds, but no result w;is 

 obtained, as some chemical change was effected in the com- 



