100 



left to right, being increased by the changes attending the prtsHce of the 

 food. 



XXIII. On the Uses of the Pylorus. The pyloric orifice is furnished 

 with a muscular ring, covered over by a fold of the mucous membrane 

 of the stomach. This kind of sphincter keeps it perfectly closed, while 

 digestion is going on in the stomach, and will not allow a free passage to 

 the food which has not yet undergone a sufficient change. The pylorus, 

 which is endowed with a peculiar and delicate sensibility, may be con- 

 sidered as a vigilant guard, which prevents any thing from passing into 

 the intestinal canal, till it has undergone the necessary changes. Seve- 

 ral authors quoted by Haller, have, very justly, observed, that the ali- 

 mentary substances do not leave the stomach in the same order that they 

 were received into it, but that they are evacuated according to their de- 

 grees of digestibility. 



One may say, that there really takes place in the stomach, a sorting of 

 the different substances which it contains. Those that are most readily 

 dissolved, get near to the pylorus, which admits them, rejecting those 

 which, not yet sufficiently digested, cannot produce on it the necessary 

 affection. To this delicacy of tact, which I ascribe to the pylorus, will 

 be objected, perhaps, the passage it allows to pieces of money and other 

 foreign indigestible substances. But these bodies, which have always 

 lain some time in the stomach, before they make their way into the in- 

 testines, repeatedly attempt the orifice of the pylorus, and pass through, 

 only when they have at last accustomed it to their contact. The gastric 

 system is under the laws of a secretory gland; and as the roots of the 

 excretory ducts, being endued with a sort of elective sensibility, will not 

 receive the secreted fluid, until it has undergone the necessary prepara- 

 tion in the glandular parenchyma, in the same manner, the pylorus ad- 

 mits aliments, and givc them passage into the intestines, which may be 

 regarded as the excretory ducia of the stomach, only when they have 

 been sufficiently elaborated by the action uf this organ. 



XXIV. As the stomach empties itself, the spaatn of the skin goes off; 

 the shivering is followed by a gentle warmth; the pulse increases in ful- 

 ness and frequency; the insensible perspiration is augmented. Diges- 

 tion brings on, therefore, a general action analogous to a febrile paroxysm; 

 and this fever of digestion, noticed already by the ancients, is particu- 

 larly observable in women of great sensibility. Nothing positive can 

 be said on the duration of stomachic digestion; food passes sooner or 

 slower from the stomach, according as its nature is such as to resist, more 

 or less, the actions which tend to dissolve it ; according too to the 

 strength and vigour of the stomach at the time, and to the activity of the 

 gastric juices. Yet we may state from three to four hours as the mean 

 time of their remaining there. It is of consequence to know the time re- 

 quired for digestion in the stomach, that we may not disturb it by baths, 

 bleedings, &c. which would call off towards other organs, those powers 

 which ought, at that time, to be concentrated upon the stomach. 



If, as is indisputable, the stomach carries with it, into its action, all the 

 other organs of the economy; if it summons to its aid, so to say, the 

 whole system of the vital powers; if this sort of derivation is the more 

 conspicuous, as the organization is more delicate, the sensibility more 

 lively, the susceptibility greater, the importance is apparent of enforcing 

 a strict diet in acute diseases, and in all cases where Nature is engaged 

 in an organic operation, which a little increase of irritation could not fail 



