72 PHILOSOPHICAL TRANSACTIONS. [aNNO 1703. 



the dura mater, by the arteries distributed through the substance of the brain; 

 the arteries which are ramified over the dura mater, at the same time con- 

 tributing in some degree to the said motion. 



Such is the experiment related by Dr. R. in his Treatise on the Anatomy of 

 the Brain ; but for further satisfaction he made the following experiment. 

 Having removed the upper part of a dog's skull he laid bare the dura mater ; 

 and, after wiping away the blood, he had a good view of that membrane, and 

 of the longitudinal sinus; whose systaltic action (which was quicker than usual) 

 exactly corresponded with the pulsations of the heart. I'his motion was ob- 

 served by himself and those who were present at the experiment, for the space 

 of a quarter of an hour; after which he thought of raising up the dura mater 

 from the brain by means of a tenaculum, and dividing it with a knife, in order 

 to examine the motion of the brain underneath. Accordingly the dura mater 

 was punctured by a tenaculum (which the dog appeared to feel sensibly, but 

 without being thrown into convulsions) ; and after the blood, which flowed 

 from this puncture, was wiped away, the systaltic motion of the cerebrum was 

 seen at the puncture, and a small clot of blood which had stuck in it was 

 thereby forced out. The point of a pair of scissars being then introduced into 

 the aperture of the dura mater, that membrane was cut transversely in the 

 part which was farthest from the longitudinal sinus ; whereupon the brain, 

 covered with the pia mater, protruded itself through this opening; the motion 

 of the dura mater being still very perceivable by the touch, and in a slight 

 degree by the sight also; notwithstanding that the elastic or contractile power 

 of its fibres had been impaired by the incision. After some hours had been 

 spent in making these observations, during which the dog had been tortured in 

 various ways and had lost much blood; at length in order to destroy all the 

 pulsific power which may be supposed to be inherent in the dura mater, or to 

 be communicated to it from some other source; it was moistened with some 

 drops of oil of vitriol, which turned it black; no contraction, however, or if any 

 a very obscure one indeed, took place; but although the dura mater was no 

 longer capable of yielding to the impulse given by the movement of the brain, 

 yet the pulsation of the brain itself could be distinctly felt on applying the 

 finger. 



All this time the dog was far from being exhausted ; but on plunging the 

 point of the knife an inch deep into the substance of the brain, he was seizcvd 

 with violent convulsions. At this time on introducing the finger into the 

 beforementioned opening made in the dura mater, the movement of the brain 

 was perceived to be stronger than before. After this a probe was pushed deeper 

 into the brain; wtiereupon the dog exhibited strong symptoms of pain ; lastly. 



