On Muscular Motion and Animal Spirits 261 



sensitive function, we need to constrict the head and 

 brain, as any one can find out in his own case : and 

 that constriction of the brain seems to proceed to 

 some extent from the harder meninges contracting 

 itself more strongly. Certainly, in great anger, when 

 we strive to the utmost of our power to repel or to 

 avenge an injury, the said membrane, as if seized 

 with convulsions, seems to constrict the brain : 

 whence it happens that the nitro-aerial spirits, forced 

 into the brain and thence into the nervous system, 

 produce certain involuntary movements and con- 

 vulsive tremors. 



I further add that it is probable that sneezing is 

 produced by the dura mater contracting itself more 

 strongly, and forcibly driving the animal spirits into 

 the nerves devoted to respiration ; for it is certainly 

 established that the membranes of the brain are 

 primarily affected in sneezing. 



Further, I am not sure whether the pulsation of the 

 heart, or even the respiration, both of which are 

 periodic, do not depend on the pulsation of the harder 

 meninges surrounding the cerebellum. 



Further, it may be held that epilepsy, as also 

 apoplexy, sometimes arise from the convulsion or 

 from the paralysis of the said membrane : for in these 

 diseases the brain itself is sometimes found free from 

 any sign of disease, and those substances which consist 

 of volatile salt and volatile sulphur, as oil of amber 

 and such like, are specially useful in these diseases : 

 for it is not to be supposed that the saline-sulphureous 

 liquids penetrate the brain itself and strengthen it, 

 inasmuch as sulphureous substances seem to be 

 hostile to the brain, and when taken too quickly, rushing 

 into the cloisters of the brain not unfrequently cause 

 convulsions, as we have elsewhere indicated. But 



