200 Mayow 



the diaphragm from its nearness and relationship 

 takes on the convulsive movement. 



It seems to be different in the case of that 

 oppression at night, with difficult respiration, which is 

 called nightmare ; for this state seems to be produced 

 not by a convulsion of the parts about the thorax but 

 by an impediment to the proper influx of spirits. 

 This oppression generally attacks those who are 

 falling asleep. For when sleep begins, the spirits 

 which are the instruments of voluntary functions, 

 retire towards the cerebrum, or at least no longer flow 

 copiously from it. Meanwhile the spirits which have 

 for their office involuntary actions and natural 

 movements issue in continual flow either from the 

 cerebrum or from the cerebellum. If, however, in 

 consequence of any confusion, or from morbid matter 

 causing disordered movement of the spirits, those of 

 the latter kind as well as the former, while sleep is 

 coming on, return towards the brain and are detained 

 there, not only voluntary, but also natural actions are 

 necessarily interrupted by the flow of spirits being 

 impeded. Hence the actions of the heart, the thorax, 

 and indeed of the whole body cease, so that the 

 patient is necessarily affected with the very greatest 

 oppression, suffocation, and a kind of immobility. 

 That this motion of the spirits is in the wrong direc- 

 tion may be inferred from this, that the parts of the 

 body, first those more remote from the brain and 

 then those nearer to it, are gradually seized with a 

 certain stiffness and weight in consequence of the lack 

 of vital spirits. Meanwhile the spirits, detained in 

 the brain and moving irregularly there, produce a 

 feeling of giddiness and a disordered imagination. 

 But when the paroxysm ceases, the spirits rush- 

 ing impetuously from the brain usually excite a 



