fome of the late Difcoveries in Science. 307 



IRRITABILITY OF THE ANIMAL FIBRE. 



Notwithftanding the many refearches made refpe£ting 

 the caufe of this irritability, much is ftill wanting. Girtan- 

 ncr afcribes it chiefly to oxygen : but the proofs which he 

 gives in fupport of his opinion do not appear fatisfa£tory j 

 fince the air does not feem to have a direct influence on. 

 the irritability of the heart. For example, if the vein of an 

 animal be opened, and if a bubble of vital air or oxygen gas 

 can be introduced into it, by means of a fmall tube, as foon 

 as the air reaches the heart the animal fends forth a cry of 

 pain and expires. Bichet, who made this experiment *, re- 

 peated it with atmofpheric air, azot, hydrogen, and the car- 

 bonic acid gas, and the animal perifhed in the like manner ; 

 but cold water injected into' a vein does not produce the 

 like effect. Bichet concludes, that the death of the animal 

 is occafipned by the interception of the air between the co- 

 lumns of the arterial and venal blood. But, in this cafe, we 

 may reft aflured that oxygen gas deftroys the animal. 



Dr. Menzies obferved, that the irritability of the heart pre- 

 ferved itfelf longer in animals ftrangled or drowned than in 

 fhofe which perifhed in gas. He thence concludes, that the 

 particular ftate which the blood acquires in pairing through 

 the lungs, and which gives it thofe fenfible qualities that 



and the fame reprefented by Muller in his Flora Danica, imder the name 

 of conferva jugdlli, which was communicated, not long ago, to the Philo- 

 matic Society at Paris. Citizens Charles and Romain Coquebert having 

 collected fome of this conferva, in the neighbourhood of Paris, afcertained 

 by means of an excellent microfcope, conftru&ed by Nairne and Blunt, 

 that in this fpecies there are male and female filaments', which unite by 

 an actual copulation ; that certain globules contained in the male filaments 

 pafs mto the interior part of the female filaments'; and that by this union 

 there arc formed in the latter feeds, or, if we may ufe the expreffion, fmall 

 »va, which reproduce the fpecies. This is the firft inltance in the ve- 

 getable kingdom of a reproduction abfolutely analogous to that which we 

 find among animals. Edit. 

 * Socicte Philom. page ijt. 



X 2 diftinguifh 



