296 DIGESTION. 



solved, in order to remark that this theory has been 

 disproved by experiments of Pavy's, in which the mucus 

 membrane of the stomachs of dogs was dissected off for a 

 small space, and, on killing the animals some days after- 

 wards, no sign of digestion of the stomach was visible. 

 "Upon one occasion, after removing the mucous mem- 

 brane and exposing the muscular fibres over a space of 

 about an inch and a half in diameter, the animal was 

 allowed to live for ten days. It ate food every day, and 

 seemed scarcely affected by the operation. Life was des- 

 troyed whilst digestion was being carried on, and the lesion 

 in the stomach was found very nearly repaired : new matter 

 had been deposited in the place of what had been removed, 

 and the denuded spot had contracted to much less than 

 its original dimensions." 



Dr. Pavy believes that the natural alkilinity of the 

 blood, which circulates so freely during life in the walls of 

 the stomach, is sufficient to neutralize the acidity of the 

 gastric juice, were it, so to speak, to make an attempt at 

 digesting parts with which it has no business ; and as may 

 be gathered from what has been previously said (p. 283), 

 the neutralization of the acidity of the gastric secretion is 

 quite sufficient to destroy its digestive powers. He also 

 very ingeniously argues that this very alkilinity must, from' 

 the conditions of the circulation naturally existing in the 

 walls of the stomach, be increased in proportion to the 

 need of its protective influence. "In the arrangement of 

 the vascular supply," he remarks "a doubly effective 

 barrier is, as it were, provided. The vessels pass from 

 below upwards towards the surface : capillaries having 

 this direction ramifv between the tubules by which the 

 acid of the gastric juice is secreted ; and being separated 

 by secretion below, must leave the blood that is proceeding 

 upwards correspondingly increased in alkilinity ; and thus, 

 at the period when the largest amount of acid is flowing 

 into the stomach, and the greatest protection is required, 



