514 



portions of blood to be supplied to different parts of the body. The 

 facts which first led the author to entertain this opinion, were the 

 accidental consequence of an extremely painful application of pure 

 kali to a wound, which occasioned a general pulsation of the limb to 

 which it was applied, although the pulsations of distant arteries were 

 at the same time undisturbed. In order to be quite certain that this 

 consequence was really dependent on the irritation of nerves, the 

 author made two experiments on rabbits in the neighbourhood of the 

 carotid artery. Having laid bare the par vagum and intercostal nerves, 

 a probe was passed under the former so as to separate it, so that the 

 irritation might be first given to this nerve alone ; but no sensible 

 effect was thus produced upon the artery. But when the same ap- 

 plication of pure kali was made to the adjacent intercostal nerve, by 

 which the artery is supplied, the dilatations and contractions of the 

 artery were considerably increased, and the violence of the pulsations 

 continued about three minutes before they began to subside. 



The same experiment being repeated on a second rabbit, was at- 

 tended with the same result ; and it w* afterwards repeated on a 

 dog without any perceptible difference. 



These visible effects of the influence which the nerves possess over 

 the arteries, enable the author to comprehend, more fully than he 

 had done before, how different supplies of blood are sent to particular 

 glands ; how various secretions come under the influence of the mind, 

 and how the internal actions of the animal economy, connected with 

 the circulation of the blood, are regulated. 



If the healthy actions in the complete animal be thus dependent 

 on nervous influence, then also the restoration of parts injured, the 

 regeneration of parts lost ; and all, even the most complicated forms 

 of disease, must be regulated by the natural or preternatural operation 

 of the same machinery. 



On the Means of producing a double Distillation by the same heat. By 

 Smithson Tennant, Esq. F.R.S. Read June 30, 1814. {Phil. 

 Trans. 1814, p. 587.] 



When steam is passed through a tube surrounded with water, it is 

 well known that it becomes condensed on the sides of the tube so 

 long as the water continues at a lower temperature than that of the 

 steam ; but since the latent heat given out in the condensation of 

 steam soon raises the temperature of the water to 212, all transfer 

 of heat ceases at that temperature, and the steam then passes un- 

 condensed. But since the temperature at which water may be raised 

 into vapour depends on the pressure of the atmosphere, the tempera- 

 ture of the surrounding water may be kept permanently lower, by 

 removing that pressure, so as permanently to act in condensing the 

 vapour of the first distillation ; and being itself raised into vapour by 

 mere transfer of the same original quantity of heat, may be received 

 as an additional product of the same process, by a suitable arrange- 

 ment of the apparatus. 



