284 Mayow 



the motion of the nitro-aerial particles ? And it tells 

 in the same direction that a muscle, like the aforesaid 

 cord, cannot be brought again to its original length 

 without the exercise of some force. And this is the 

 reason why a cramp is wont to be produced in a 

 muscle when its antagonist is paralysed. For when 

 a muscle is once contracted, it will remain in that 

 state until it has been restored to its former length 

 by the pull of its antagonist. 



From this hypothesis of ours it is not difficult to 

 understand how it is that when the motor parts have 

 been struck by lightning they are not unfrequently 

 convulsed, and remain tense, although the skin 

 surrounding the muscles is often uninjured. For I 

 have tried to show above that the nitro-aerial particles, 

 not only those in the brain but also those in the 

 motor parts, are sometimes as it were set on fire when 

 struck by lightning : nay, the nitro-aerial particles 

 thrown into an almost igneous motion, twist and 

 wrench the fibrils so violently that they cannot again 

 be drawn out, but will remain always tense ; just as it 

 would happen to the above-mentioned string if it 

 were brought too near the flame of the lamp. 



OF THE MOTION OF CONTRACTING MUSCLES 



Now that we have in this way considered how 

 muscular contraction is caused, it remains for us to 

 enquire shortly as to the motion of the muscles as 

 they contract, and also that of the parts attached to 

 them : but that this matter may be more clearly 

 understood, I shall premise the following. 



In the first place, we lay it down that if any string 

 with both ends free contracts uniformly, both of its 

 ends will be drawn towards the centre. 



