world; as well those of the vessels, which circulate their juices, and of
the muscles, which perform their locomotion, as those of the organs of
sense, which constitute their ideas.

This last class of motion is the subject of the following pages; which,
though conscious of their many imperfections, I hope may give some pleasure
to the patient reader, and contribute something to the knowledge and to the
cure of diseases.

* * * * *

SECT. II.

EXPLANATIONS AND DEFINITIONS.

I. _Outline of the animal economy._--II. 1. _Of the sensorium._ 2. _Of
the brain and nervous medulla._ 3. _A nerve._ 4. _A muscular fibre._ 5.
_The immediate organs of sense._ 6. _The external organs of sense._ 7.
_An idea or sensual motion._ 8. _Perception._ 9. _Sensation._ 10.
_Recollection and suggestion._ 11. _Habit, causation, association,
catenation._ 12. _Reflex ideas._ 13. _Stimulus defined._

* * * * *

As some explanations and definitions will be necessary in the
prosecution of the work, the reader is troubled with them in this
place, and is intreated to keep them in his mind as he proceeds, and to
take them for granted, till an apt opportunity occurs to evince their
truth; to which I shall premise a very short outline of the animal
economy.