84? DIGESTION. 



hour-glass contraction in a living dog, and remarked the peristaltic 

 motion to be much more vigorous in the pyloric half. b 



Van Helmont asserted that the food becomes sour by digestion, 

 but this was afterwards denied, and acidity said never to happen 

 except in cases of disorder. Sir Gilbert Blane, many years ago, 

 however, declared that he had " satisfied himself that there is 

 such an acid (the gastric) by applying the usual tests to the 

 inner surface of the stomach of animals. This property in rumin- 

 ating animals," he added, " is confined to the digesting stomach." 6 

 Dr. Prout has discovered that the acid generated is the muriatic, 

 both free and in combination with alkalies. d Tiedemann and 

 Gmelin soon afterwards found the same thing, though without 

 knowing, they assure us, Dr. Prout's discovery. They assert the 

 clear ropy fluid of the stomach, or gastric juice, without food, to 

 be nearly, or entirely, destitute of acidity, while the presence of 

 food, or of the most simple stimulus to the mucous membrane, 

 occasions it to become acid, and more so, according to the greater 

 indigestibility of the food. The acid is very copious. They also 

 assert the presence of acetic acid ; but Dr. Prout believes this to 

 be either the result of irritation or of disease, or occasionally to 

 be derived from the aliment, and consequently to be neither 

 necessary nor ordinary. The general change of the aliment in the 

 stomach appears a greater or less approach to the nature of albu- 

 men, but Dr. Prout has been unable to detect true and perfect 

 albumen there when none has been taken. 



Brutes have been the subjects of these experiments ; chiefly 

 the rabbit, horse, dog, and cat. 



Besides the labours of Dr. Prout, and of the professors of 

 Heidelberg, a work has been published on all the subjects of 

 chymification and chylification by MM. Leuret and Lassaigne, 

 contradictory in many respects to the results of the others ; but, 

 knowing as I do the extreme accuracy of Dr. Prout in experi- 

 menting and deducing, and seeing that Tiedemann and Gmelin 

 have bestowed infinite labour in repeating, varying, and extend- 



b Transactions of the Medical Society of London, vol. ii. 1788. In the lion, 

 bear, &c., the stomach is usually found divided by a slight contraction at its 

 middle, and in some animals of the mouse kind by a slight elevation of its inner 

 coat. 



e Transactions of a Society for the Improvement of Medical and Surgical Know- 

 ledge, vol. ii. p. 138. sq. 



Phil. Trans. 1824. 



