Their causes have made the subject of this fourth part.
FOOTNOTES: [29] Part I.sect.

7.
[30] Part I.sect.

10.
[31] I do not here enter into the question debated among physiologists, whether pain be the effect of a contraction, or a tension of the nerves.
Either will serve my purpose; for by tension, I mean no more than a violent pulling of the fibres which compose any muscle or membrane, in whatever way this is done.
[32] Part II.sect.

2.
[33] Part II.sect.

1.
[34] Part I.sect.7.