THE PHYSIOLOGY OF DIGESTION 179 



The gastric fluid of man and that of frogs and snakes agree perfectly in 

 their action on flesh, as the experiments of Spallanzani prove that the first of 

 these powerfully dissolves meat out of the body. As the menstruum of the two 

 latter animals acted so uniformly on bones, it appeared highly probable the 

 fluid of our own stomach would also. To ascertain this, the condyles of the 

 thigh bone of a chicken, weighing eleven grains, were swallowed; the bone 

 remained a considerable time in the stomach, as was supposed from some uneasy 

 sensations that were occasionally experienced for between two and three days; 

 the fourth day it was discharged, reduced to a shell, weighing only three grains. 

 Thus far the digestion of man and these animals perfectly agree, in solution 

 being the first step towards the conversion of food into chyle; but they differ 

 in some particulars, and probably by attending to these, they may be of use to us. 

 First. They are cold-blooded animals: heat is a powerful agent in all solu- 

 tions, and the experiments of Spallanzani prove it greatly assists the action of 

 the gastric liquor out of the stomach. 



Secondly. They do not masticate their food. 



These two inconveniences are obviated, by these animals never drinking 

 when their digestion is going on, so that their fluid acts in its undiluted state; 

 whereas in man, it is always diluted, as he seldom eats without drinking. That 

 this was the case with these animals I had clear proof; for although I examined 

 the contents of their stomachs so often, in no one case could I find any fluid 

 more than a jelly-like substance, appearing to be made up of gastric juice and 

 dissolved flesh. Supposing, however, that the pressure used in bringing up the 

 food of the frogs might have forced the more fluid parts into the duodenum, 

 I resolved to ascertain the fact in another way; this was easily done. A tea- 

 spoon could readily be passed into their stomachs, and with this the dissolved 

 food could all be brought up; it was always, however, of the consistence above 

 mentioned. During the time these experiments were made, they were constantly 

 kept in large jars of water. The attention to this circumstance by these animals, 

 which swallow their prey entire, is a necessary part in their digestion, as they 

 require a very powerful menstruum, so as to dissolve not only entire muscles, 

 but also bones. The inference we would draw from it would be, to attend occa- 

 sionally to what necessity urges them to observe constantly. Thus when our 

 stomachs are weak, or we are troubled with dyspeptic symptoms, like them we 

 ought to avoid much diluting our gastric juice; so that although it were 

 secreted not perfectly healthy, yet having the advantage of acting in its uncom- 

 bined state, solution and digestion may go on, when it otherwise would not, 

 with the common quantity of drink. Indeed our stomachs in this respect act 

 a kind part to us; for when we make our first dish on broth it seldom relishes 

 much solid aliment after it; hence soups are the first dish at the table of the 

 temperate, and the last at that of the epicure. 



Both Spallanzani and Eeaumur believed that vegetable food is less 

 easily digested by certain animals than meat. Young reinvestigated 

 this question on frogs. He found that when peas, beans, wheat and 

 bread enclosed in linen bags were introduced into the stomach, all but 

 the bread were still entire at the end of thirty hours; but when the 

 peas and beans were well bruised before introduction they were dis- 

 solved. The author concludes that the living 'principle in the seeds 

 resists digestion. In harmony with this view he found that seeds 

 would germinate when retained in the stomach. An entertaining 

 story is cited from the Italian anatomist Morgani. 



