Book 3
8
Now the constitution of the organs might itself suffice to give a naturalist an indication of their functions. For Nature would never have purposelessly constructed the oesophagus of two coats with contrary dispositions; they must also have each been meant to have a different action. The Erasistratean school, however, are capable of anything rather than of recognizing the effects of Nature. Come, therefore, let us demonstrate to them by animal dissection as well that each of the two coats does exercise the activity which I have stated. Take an animal, then; lay bare the structures surrounding the gullet, without severing any of the nerves,Under the term neura, tendons were often included as well as nerves. Similarly in modern Dutch the word zenuw ( sinew) means both a tendon and a nerve; zenuachtig = nervous. arteries, or veins which are there situated; next divide with vertical incisions, from the lower jaw to the thorax, the outer coat of the oesophagus (that containing transverse fibres); then give the animal food and you will see that it still swallows although the peristaltic function has been abolished. If, again, in another animal, you cut through both coatsRather than the alternative reading, τὸν ἔσωθεν χιτῶνα. Galen apparently supposes that the outer coat will not be damaged, as the cuts will pass between its fibres. These cuts would be, presumably, shor ones, at various levels, no single one of them involving the whole circumference of the gullet. with transverse incisions, you will observe that this animal also swallows although the inner coat is no longer functioning. From this it is clear that the animal can also swallow by either of the two coats, although not so well as by both. For the following also, in addition to other points, may be distinctly observed in the dissection which I have described — that during deglutition the gullet becomes slightly filled with air which is swallowed along with the food, and that, when the outer coat is contracting, this air is easily forced with the food into the stomach, but that, when there only exists an inner coat, the air impedes the conveyance of food, by distending this coat and hindering its action.
