10^ 



OF THE VESSELS 



of the cheek ; enters by that hole, which is a complete per- 

 foration of the buccinator muscle, into the moutli ; and tliere 

 discharges its fluid very copiously. 



V. Another exquisite structure, differing indeed from 

 the four preceding instances, in that it does not relate to 

 the conveyance of fluids, but still belonging, like these, to 

 the class of pipes or conduits of the body, is seen in the 

 larynx. (PI. XXI. fig. 1, 2.) We all know, that there go 

 down the throat two pipes, one leading to the stomach, the 

 other to the lungs ; the one being the passage for the food, 

 the other for the breath and voice : we know also that both 

 these passages open into the bottom of the mouth ; the gullet, 

 necessarily, for the conveyance of the food ; and the wind- 

 pipe, for the speech and the modulation of sound, not much 

 less so : therefore, the difficulty was, the passages being so 

 contiguous, to prevent the food, especially the liquids, which 

 we swallow into the stomach, from entering the wind-pipe, 

 i. e. the road to the lungs ; the consequence of which er- 

 ror, when it does happen, is perceived by the convulsive 

 throes that are instantly produced. This business, which 

 is very nice, is managed in this manner. The gullet (the 

 passage for food) opens into the mouth like the cone or 

 upper part of a funnel, the capacity of which forms indeed 

 the bottom of the mouth. Into the side of this funnel, at 

 the part which lies the lowest, enters the wind-pipe, by a 

 chink or slit, with a lid or flap, like a little tongue, accu- 

 rately fitted to the orifice. The solids or liquids which we 

 swallow, pass over this lid or flap, as they descend by the 

 funnel into the gullet. Both the weight of the food, and 

 the action of the muscles concerned in swallowing, con- 

 tribute to keep the lid close down upon the aperture, whilst 

 any thing is passing ; whereas, by means of its natural car- 

 tilaginous spring, it raises itself a little, as soon as the food 

 is passed, thereby allowing a free inlet and outlet for the 

 respiration of air by the lungs. And we may here remark 

 the almost complete success of the expedient, viz. how sel- 

 dom it fails of its purpose, compared with the number of in- 

 stances in which it fulfils it. Reflect, how frequently we 

 swallow, how constantly we breathe. In a city feast, for 

 example, what deglutition, what anhelation ! yet does this 

 little cartilage, the epiglottis, so effectually interpose its of- 

 fice, so securely guard the entrance of the wind-pipe, that, 

 whilst morsel after morsel, draught after draught, are cours- 

 ing one another over it, an accident of a crumb or a drop 

 slipping into this passage, (which nevertheless must be 



