Same two faculties seen in stomach. Gurglings or borborygmi show that this organ is weak and is not gripping its contents tightly enough. Undue delay of food in a weak [Pg li] stomach proved not to be due to narrowness of pylorus: length of stay depends on whether digestion (another instance of the characteristically vital process of alteration) has taken place or not. Erasistratus wrong in attributing digestion merely to the mechanical action of the stomach walls. When digestion completed, then pylorus opens and allows contents to pass downwards, just as os uteri when development of embyro completed.
Chapter [V]
If attraction and elimination always proceeded pari passu, the content of these hollow organs (including gall-bladder and urinary bladder) would never vary in amount. A retentive faculty, therefore, also logically needed. Its existence demonstrated. Expulsion determined by qualitative and quantitative changes of contents. “Diarrhoea” of stomach. Vomiting.
Chapter [VI]
Every organic part has an appetite and aversion for the qualities which are appropriate and foreign to it respectively. Attraction necessarily leads to a certain benefit received. This again necessitates retention.
Chapter [VII]
Interaction between two bodies; the stronger masters the weaker; a deleterious drug masters the forces of the body, whereas food is mastered by them; this mastery is an alteration, and the amount of alteration varies with the different organs; thus a partial alteration is effected in mouth by saliva, but much greater in stomach, where not only gastric juice, but also bile, pneuma, innate heat (i.e. oxidation?), and other powerful factors are brought to bear on it; need of considerable alteration in stomach [Pg lii] as a transition-stage between food and blood; appearance of faeces in intestine another proof of great alteration effected in stomach. Asclepiades’s denial of real qualitative change in stomach rebutted. Erasistratus’s denial that digestion in any way resembles a boiling process comes from his taking words too literally.
Chapter [VIII]
Erasistratus denies that the stomach exerts any pull in the act of swallowing. That he is wrong, however, is proved by the anatomical structure of the stomach—its inner coat with longitudinal fibres obviously acts as a vis a fronte (attraction), whilst its outer coat exercises through the contraction of its circular fibres a vis a tergo (propulsion); the latter also comes into play in vomiting. The stomach uses the oesophagus as a kind of hand, to draw in its food with. The functions of the two coats proved also by vivisection. Swallowing cannot be attributed merely to the force of gravity.