542 PRACTICE OF PHYSIC. 



ation of the exciting causes, because one of the most remarkable 

 is fever, and other cases of determination to the brain. We con- 

 clude, that one of the most frequent causes is the turgescence 

 or increased impetus of the blood in the vessels of the brain. 



u This brings us back to the question, Whether the external 

 headach is a concurrence with or a consequence of the internal ? 

 and we think it most commonly the latter. The internal parts are 

 certainly the most sensible ; there are many causes which can 

 only act directly upon them ; and we have many proofs of the 

 connexion that allows causes acting internally to be communi- 

 cated to the external parts. 



" We have thus given a general idea, admitting of various 

 modifications, which we must not enter upon at present. 



" The Case in hand is one of external headach from an internal 

 cause. This last, we conclude, from the double vision attend- 

 ing it. The cause of double vision we refer to the unequal 

 motion of the two eyes, so that the object is not seen in the 

 same place by both eyes. This we suppose fully demonstrated 

 by Dr. Porterfield, and in this case to depend upon a degree of 

 palsy or spasm in the muscles of the eye. This might be sup- 

 posed to be an affection of the muscles communicated from the 

 neighbouring parts, but is more probably an affection of their 

 nerves from an internal cause. 



" Here I think the internal cause is discovered by the double 

 vision only happening on the inclination of the head forward, 

 which, by opposing the gravity to the direction of the blood, re- 

 tards its motion ; and it may do this in the external as well as 

 internal parts, but not so considerably in the first as in the 

 last. The peculiar distribution of the venous blood of the ence- 

 phalon, and its accumulation in the sinus, gives occasion to stag- 

 nation ; particularly the motion in the sinus being from before 

 backwards, gives occasion to stagnation upon inclination of the 

 head forward. I have known a case of moderate stooping pro- 

 duce a temporary fit of apoplexy. 



" Vertigo and Scotomia also, which occurred in this instance, 

 are known to arise from compression. I have known them 

 frequently produced by inclining the head forward. 



" We have no doubt, therefore, that in the present case there is 

 uch a topical affection in the interior part of the brain, as gives oc- 



