208 The Physiology of Digestion [lect. 



consisting of glands which, very obvious in birds, are not so 

 evident in man ; but he thinks that these glands furnish the 

 mucus of the stomach only, the true gastric juice, succus 

 gastricus, ventriculi succus, being secreted by the arteries. 

 The more exact knowledge of nervous action, which, owing 

 largely to his own labours, had been gathered in since Boer- 

 haave's days, led him to discard the idea that a nervous fluid, 

 oozing from the endings of the nerves, intervenes in gastric 

 digestion. 



Dwelling on the difficulty of obtaining gastric juice in a 

 pure condition, noting that acidity is often a token of the 

 onset, and alkalinity of the advance of putrefaction, he concludes 

 that pure gastric juice is neither acid nor alkaline ; and while 

 speaking of it as a macerating liquor which softens and dissolves 

 the food, he refuses to regard it as a ferment. It is not a 

 corrosive liquid, as are many acids, and though it may be at 

 times acid, the acidity is a token of the degeneration of the 

 digested food, not of digestion itself, which "imparts to the 

 " food a wholesome animal nature," i.e. gives it the beginning of 

 vitality; and the characteristic of living animal tissues is, he 

 urges, alkalinity rather than acidity. 



Trituration he regards as a useful aid, especially where 

 hard grains form a part of food, as in that of birds, but only an 

 aid. " They have done well who have brought back to its 

 "proper mediocrity the power of trituration so immensely 

 " exaggerated." 



His account of bile shews how much advance had taken 

 place, through repeated quiet work, in the preceding years. 

 Bile he insists is not as some have thought a mere excrement. 

 Retained for a while and slightly altered during its stay in 

 but not formed by the gall-bladder, secreted on the contrary 

 by the substance of the liver, partly perhaps from the blood 

 supplied by the hepatic artery but mainly from that of the 

 vena porta, bile is a fluid viscid and bitter but not acid, and 

 indeed not alkaline, a fluid which as all know has the power 

 of dissolving fat and so acts on a mixture of oil and water 

 as to form out of them an emulsion ; it thus dissolves all the 

 food into the homogeneous magma which is called chyle. If, 



