BOOK III
Chapter [I]
A recapitulation of certain points previously demonstrated. Every part of the animal has an attractive and an alterative (assimilative) faculty; it attracts the nutrient juice which is proper to it. Assimilation is preceded by adhesion (prosphysis) and that again, by application (prosthesis). Application the goal of attraction. It would not, however, be followed by adhesion and assimilation if each part did not also possess a faculty for retaining in position the nutriment which has been applied. A priori necessity for this retentive faculty.
Chapter [II]
The same faculty to be proved a posteriori. Its corresponding function (i.e. the activation of this faculty or potentiality) well seen in the large hollow organs, notably the uterus and stomach.
Chapter [III]
Exercise of the retentive faculty particularly well seen in the uterus. Its object is to allow the embryo to attain full development; this being completed, a new faculty—the expulsive—hitherto quiescent, comes into play. Characteristic signs and symptoms of pregnancy. Tight grip of uterus on growing embryo, and accurate closure of os uteri during operation of the retentive faculty. Dilatation of os and expulsive activities of uterus at full term, or when foetus dies. Prolapse from undue exercise of this faculty. Rôle of the midwife. Accessory muscles in parturition.
Chapter [IV]
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.
Chapter [IX]
These four faculties which subserve nutrition are thus apparent in many different parts of the body.
Chapter [X]
Need for elaborating the statements of the ancient physicians. Superiority of Ancients to Moderns. This state of affairs can only be rectified by a really efficient education of youth. The chief requisites of such an education.
Chapter [XI]
For the sake of the few who realty wish truth, the argument will be continued. A third kind of fibre—the oblique—subserves retention; the way in which this fibre is disposed in different coats.
Chapter [XII]
The factor which brings the expulsive faculty into action is essentially a condition of the organ or its contents which is the reverse of that which determined attraction. Analogy between abortion and normal parturition. Whatever produces discomfort must be expelled. That discomfort also determines expulsion of contents from gall-bladder is not so evident as in the case of stomach, uterus, urinary bladder, etc., but can be logically demonstrated.
Chapter [XIII]
Expulsion takes place through the same channel as attraction (e.g., in stomach, gall-bladder, uterus). Similarly the delivery (anadosis) of nutriment to the liver from the food-canal viâ the mesenteric veins may have its direction reversed. Continuous give-and-take between different parts of the body; superior strength of certain parts is natural, of others acquired. When liver contains abundant food and stomach depleted, latter may draw on former; this occurs when animal can get nothing to eat, and so prevents starvation. Similarly, when one part becomes over-distended, it tends to deposit its excess in some weaker part near it; this passes it on to some still weaker part, which cannot get rid of it; hence deposits of various kinds. Further instances of reversal of the normal direction of anadosis from the food canal through the veins. Such reversal of functions would in any case be expected a priori. In the vomiting of intestinal obstruction, matter may be carried backwards all the way from the intestine to the mouth; not surprising, therefore, that, under certain circumstances, food-material might be driven right back from the skin-surface to the alimentary canal (e.g. in excessive chilling of surface); not much needed to determine this reversal of direction. Action of purgative drugs upon terminals of veins; one part draws from another until whole body participates; similarly in intestinal obstruction, each part passes on the irritating substance to its weaker [Pg liv] neighbour. Reversal of direction of flow occurs not merely on occasion but also constantly (as in arteries, lungs, heart, etc.). The various stages of normal nutrition described. Why the stomach sometimes draws back the nutriment it had passed on to portal veins and liver. A similar ebb and flow in relation to the spleen. Comparison of the parts of the body to a lot of animals at a feast. The valves of the heart are a provision of Nature to prevent this otherwise inevitable regurgitation, though even they are not quite efficient.
Chapter [XIV]
The superficial arteries, when they dilate, draw in air from the atmosphere, and the deeper ones a fine, vaporous blood from the veins and heart. Lighter matter such as air will always be drawn in preference to heavier; this is why the arteries in the food-canal draw in practically none of the nutrient matter contained in it.
Chapter [XV]
The two kinds of attraction—the mechanical attraction of dilating bellows and the “physical” (vital) attraction by living tissue of nutrient matter which is specifically allied or appropriate to it. The former kind—that resulting from horror vacui—acts primarily on light matter, whereas vital attraction has no essential concern with such mechanical factors. A hollow organ exercises, by virtue of its cavity, the former kind of attraction, and by virtue of the living tissue of its walls, the second kind. Application of this to question of contents of arteries; anastomoses of arteries and veins. Foramina in interventricular septum of heart, allowing some blood to pass from right to left ventricle. Large size of aorta probably due to fact that it not merely carries the pneuma received from the lungs, but also some of the blood which percolates through septum from right ventricle. Thus arteries carry not merely pneuma, but also some light vaporous blood, which certain parts need more [Pg lv] than the ordinary thick blood of the veins. The organic parts must have their blood-supply sufficiently near to allow them to absorb it; comparison with an irrigation system in a garden. Details of the process of nutrition in the ultimate specific tissues; some are nourished from the blood directly; in others a series of intermediate stages must precede complete assimilation; for example, marrow is an intermediate stage between blood and bone.
From the generalisations arrived at in the present work we can deduce the explanation of all kinds of particular phenomena; an instance is given, showing the co-operation of various factors previously discussed.