284 EEVIEWS. 



produced by a contraction of the blood-vessels, due to an action in the 

 nervous system, and not to general loss of temperature affecting the 

 blood of the system generally. Besides, it was observed that, the 

 greater the pain produced in the arm immersed in the cold water, the 

 more the temperature was diminished in the hand left in the air. 

 But other proofs are not wanting that the action of the nervous 

 system is, in this way, sufficient to dimmish the calibre of blood-vessels. 

 "We have ourselves performed the following modification of the fore- 

 going experiment. A bat is placed upon a small piece of board and 

 fastened with both wings fully expanded, so that one, say the right, 

 can be readily inspected with a microscope. As the web of the bat's 

 wing is generally too much darkened with pigment to admit of very 

 precise observation of the blood-vessels, it is necessary to peel off some 

 of the epidermis, which is easily done by seizing a portion of it with 

 a pair of forceps over one of the metacarpal ribs of the wing and so 

 tearing gently off a small portion : in the portion thus denuded an 

 artery and accompanying vein are to be sought, and the former accu- 

 rately measured with an eyepiece micrometer. If then a small muslin 

 bag of snow, or powdered ice and salt, be applied to the other wing, in 

 a short time, we may observe the artery under observation diminish- 

 ing very remarkably in calibre, and indeed, under favourable circum- 

 stances, becoming almost entirely closed ; as we have seen in a bat 

 which had been flying about in a small room, the upper part of which 

 was very warm in consequence of the burning of gas in it ; the animal 

 was consequently warm and its circulation very active at the moment 

 of the commencement of the experiment. 



On the announcement, therefore, of Bernard's discovery on section 

 of the cervical sympathetic, Brown-Sequard was prepared to expect 

 that the irritation of the divided sympathetic by galvanism would pro- 

 bably be followed by constriction of the blood-vessels and the very 

 reverse phenomena of those observed to follow the section ; and he, 

 in America, and a couple of months later, Bernard, in Paris, announced 

 this important discovery to the scientific world, while Dr. Augustus 

 "Waller, though ignorant of the publications of either of the former 

 experimenters, communicated the same discovery to the " Academie 

 des Sciences." 



There is no doubt that the knowledge of the effects of paralysis 

 and of irritation of the sympathetic nerve, thus obtained, opened a 

 new and most important field for physiological investigation, indeed, 

 it is one in which many labourers have already toiled with success. 

 The immediate connexions and relations of the sympathetic to the 

 cerebro-spinal axis had, it is true, been already tolerably well inves- 

 tigated by anatomists, but the presiding influence exercised over 

 the heart, blood-vessels, and indeed over involuntary muscular fibre 

 generally, by the nervous system, had not been studied with suc- 

 cess by physiologists : the vast importance of the sympathetic system 

 in its union with the cerebro-spinal axis had not been fully recognized: 

 nor had any real attempt been made to explain many of the principal 





