OF THE EXTERNAL SENSES. 3o9

before experience, make its mouth, as we fay,water for that food.

That numerous divifion of animals which Lin-nasus ranks under the clafs of worms, have, fcarce-ly any of them, any head. They neither fee norhear, have neither eyes nor ears; but many ofthem have the power of felf-motion, and appearto move about in fearch of their food. They canbe directed in this fearch by no other fenle thanthat of Smelling. The moft accurate microfcopi-cal obfervations, however, have never been ableto difcover in fuch animals any diltindt organ ofSmell . They have a mouth and a ltomach , butno noftrils. The organ of Tafte, it is probable,has in them a fenfibility of the fame kind with thatwhich the olfactory nerves have in more perfectanimals. They may, as it were, tafte at a diftance,and be attracted to their food by an affectionof the fame organ by which they afterwards en-joy it; and Smell and Tafte may in them be nootherwife diftinguillied than as weaker or ftrongerfenfations derived trom the fame organ.

The fenfations of Heat and Cold, when excitedby the prefiure of fome body either heated orcooled beyond the adtual temperature of our ownorgans, cannot be faid, antecedently to obferva-tion and experience, inftinftively to fuggelt anyconception of the folid and refilling fubftancej which excites them. What was faid of the l'enfeof Talte may very properly be faid here. Beforewe can feel thofe fenfations, the prefiure ot theexternal body w r hich excites them mult neceffarily