246 Mayow 



mind, and mutually agitated in most rapid motion. 

 And this is further confirmed by this, that for the con- 

 traction of the muscles there is, as we have indicated 

 above, absolute need, not only of animal spirits, 

 brought by the nerves from the brain, but in addition, 

 of other particles supplied by the blood. 



Let us now consider, then, what is the nature of 

 those particles by means of which muscular motion is 

 effected. As to this, the most commonly accepted 

 opinion is that muscular motion depends upon salts 

 of different kinds, mixed together and mutually effer- 

 vescing in the motor parts. For indeed it is neces- 

 sary for setting up effervescence of this kind, that one 

 of these salts should be of an acid character, but the 

 other purely saline, fixed or volatile ; but it is indeed 

 probable that an acid salt never exists in the mass 

 of the blood except in case of disease, inasmuch 

 as, when in a state of health, it is impregnated only 

 with volatile, or it may be acido-saline salt, such as 

 the ammoniacal salt. Besides, it is scarcely to be sup- 

 posed that an acid salt has a place in the motor parts, 

 because all acids are directly hostile to the tender 

 and delicate structure of the fibrils, and they would 

 be much injured by an acid liquid poured on them. 

 Furthermore, when these opposed salts, of whatever 

 sort they be, come from the mass of the blood, what 

 would prevent them, mixed in the blood, from acting 

 on each other, and, as contrary salts do, destroying 

 each other ? And to these considerations we may 

 add that the effervescence of contrary salts would not 

 by any means be suitable for the motor parts, inas- 

 much as contrary salts mixed together do not com- 

 bine without coagulation, but yet coagulation can by 

 no means be admitted in the very minute structure of 

 the fibrils. Nor should we omit to notice this, that 



