tOL. XXIII.] PHILOSOPHICAL TRANSACTIONS. 73 



on thrusting the whole knife quite to the opposite side of the brain, the most 

 horrible convulsions were excited ; yet even at this time both Dr. R. and his 

 attendants could feel very distinctly the alternate elevation and depression of the 

 brain, on introducing their fingers. 



Hence Dr. R. infers that no doubt can remain respecting the proximate cause 

 of* the aforesaid motion.* 



Account of a Booh, intituled. Consilium JEtiologicum De Casu quodam Epilep- 

 tico: quo rcspondelur Epistol^ Docliss. Ftri Thomce Hobart, M. D. Annexa 

 Disquisitione de Perspirationis Jnsensibilis Materia, et Peragendce Ralione. 

 Authore Gulielmo Cole, M. D. N° 287, p. 1485. 



Dr. Cole supposes the seat of epilepsy to be " in the cortical part of the brain, 

 close to where the medullary part begins ; at which place he thinks the nutri- 

 tious juice, newly separated from the blood, but happening to be somewhat 

 more gross than usual, meets with a check in its progress, on account of the 

 natural coarctation of the vessels here at their passing into the medullary part ; 

 so that the protrusion being continual, it must undergo some congestion, and 

 in some measure distend this repository ; whence it gradually becomes maturated 

 into a ferment, which acquiring a certain degree of acrimony, breaks forth into 

 the continued channels of the medullary part, and by vellicating them, produces 

 the first symptoms of the disorder ; and as this offending matter is further pro- 

 pagated along the tracts of the nerves and fibres, the other symptoms take 

 place. 



* The alternate elevation and depression of the brain and dura mater, is a subject in the explana- 

 tion of which physiologists have widely differed. See Haller's Element. Physiologiae, torn. iv. lib. x. 

 ^ xxxviiij xxxix, xli, et seq. wliere the principal authorities on both sides are referred to. Baglivy's 

 hypothesis of an original syslaliic power belonging to the dura mater itpelf, and resembling that of the 

 heart, has been long since abandoned ; and the only question has been whether the cerebral move- 

 ments correspond with the systole and diastole of the heart, or with the dilatation and contraction 

 of the lungs ? This last circumstance, although it wa« overlooked by Dr. Ridley, is now regarded as 

 the principal cause of this phenomenon. For it has been found that the brain and dura mater are 

 distended or elevated in the act of expiration (i. e. when, from the collapsed state of the lungs, an 

 impediment is opposed to ihe free transmission of the blood through them, and the blood is therefore 

 accumulated in the right cavities of the heart, in the superior vena cava, and consequently in the 

 vessels of the brain) ; and on the other hand, that those parts, (viz. the brain and its investing mem- 

 branes,) are depressed or subside during the act of inspiration, i. e. when a free passage being 

 restored to the blood through the lungs, the pievious accumulation in the right cavities of the heart, 

 in the vena cava, and consequently in ihe blood vessels of the head, is removed. This alternate ele- 

 vation and depression of the brain, and its membranes, corresponding with the times of expiration 

 and inspiration, must not be confounded with the pulsatory action which the encephalic arteries 

 possess, in common with the arteries distributed to other parts of the body. 

 VOL. V. L 



