266 Mayow 



scarcely any remain in the brain to perform the 

 voluntary functions and sensation, whence it is that 

 we can hardly keep awake. 



But, now, as the animal spirits consist of nitro- 

 aerial particles, there will be no difficulty in under- 

 standing how the effects just described are produced 

 by them in the stomach. For although the nitro- 

 aerial spirit is not acid, still iron is corroded by it 

 and vitriols produced, fixed salts are liquefied, and the 

 structures of things are dissolved as by a universal 

 solvent, as I have elsewhere endeavoured to show. 

 It therefore seems established that the much-talked- 

 of ferment of the stomach consists chiefly of nitro- 

 aerial particles, which, deposited in the membranes 

 of the stomach by the nerves, are probably there mixed 

 with a suitable liquid secreted from the blood by 

 means of the glandular membranes of the stomach ; 

 and that the fermentative liquid of the stomach is 

 composed of both of them brought into its .cavity 

 by special vessels. And hence we may seek the 

 reason why serene and rather thin air so much tends 

 to sharpen the appetite and to promote digestion, 

 as has been found by common experience, while 

 when the air is thicker and loaded with noxious 

 vapours it soon produces discomfort in the stomach. 

 To these I further add, that from the swimming- 

 bladder which in many fishes has been found filled 

 with an aerial substance, there is an open passage 

 into the stomach — certainly a probable indication 

 that something aerial conduces to the digestion of 

 food, as has been remarked by the learned Dr Walter 

 Needham. Indeed, as fishes take only a small 

 quantity of air out of the water, it would seem 

 necessary that the aerial ferment should be stored in 

 some receptacle from which it may be brought in 



