250 Mayow 



moving themselves in the motor parts. But now of 

 these particles by which muscular contraction is pro- 

 duced, some, viz. the animal spirits, are brought into 

 the motor parts from the brain by means of the 

 nerves ; while others are supplied from the mass of 

 the blood ; as we have shown above. Let us now see 

 whether the nitro-aerial particles are those motive 

 particles supplied from the blood, or, on the other 

 hand, are those coming from the brain — that is, the 

 animal spirits. On this point I was for some time 

 in doubt whether the nitro-aerial particles go im- 

 mediately from the blood into the motor parts ; but 

 on serious consideration of the matter it seems more 

 probable that the motive particles supplied from the 

 blood are of a saline-sulphureous kind, as to some 

 extent appears from what has been said above : 

 whence it follows that the nitro-aerial particles come 

 from the brain, and consequently are themselves the 

 animal spirits. Indeed, it is much more probable that 

 the nitro-aerial spirit should come from the brain 

 than that saline-sulphureous particles should do so. 

 For sulphureous particles do not occur at all in the 

 brain, whereas they are disseminated everywhere 

 throughout the mass of the muscles. Indeed, sul- 

 phureous matters seem to be hostile to the animal 

 spirits ; for, liquors full of volatile sulphur, such as 

 spirit of wine and the chemical oils of vegetables, 

 when taken too quickly disturb the brain and 

 the animal spirits, and produce not only drunken- 

 ness, but not rarely madness and fatal convulsions. 

 While on the contrary the structure of the brain 

 seems to be such as to render it specially fit for 

 separating the nitro-aerial spirit from the blood and 

 for preserving it, as will be more fully stated below. 

 As to the nature of the animal spirits, the authority 



