Chap. 3 1 .} Balls of Hair m Stomachs cf Animals. 3 1 9 

 grains loft eight in twenty-four hours, and in three 

 days were totally diffolved. Grain and fruit expoicd 

 to the fame procefs, were very little if" at all affected. 

 Digeftion, therefore, in birds of prey is performed 

 by a fluid, which acts only upon animal matter. This 

 - fluid is very abundant in the ftomachs of thefe ani- 

 mals. Small pieces of fponge, of thirteen grains, {hut 

 up in the tubes, weighed three grains more when 

 thrown up. 



Notwithftanding thefe effects of the digeftive or- 

 gans, the motions of the flomach and the gizzard arc 

 fcarcely perceptible. There is reafon, however, to 

 believe, that the little motion they have is very re- 

 gular. On examining the furfabe of the balls of hair 

 which are found in the ftomachs of animals which 

 lick their coats, the hairs in each hemifphere feem to 

 arife from a center, and to have the fame direction, 

 which is circular, and correiponding with what would 

 appear to be the axis of motion. This regularity in 

 the direction of the hair could not be produced if 

 there was not a regularity in the motion of the ftomach. 

 The fame is proved in fome birds, as the cuckow, 

 which fometimes feeds on hairy caterpillars. 



The principal inftrnment of digeftioh in rrtoft ani- 

 mals, is however now generally fuppofed to be the 

 gaftric juice ; a fluid which diftils from certain glands, 

 fittiated in the coats of the ftomach, nnd mixes with 

 the food as foon as it is received into that organ. 



The Abbe Spalanzani, in order to obtain a fight of 

 the gaftric juice, introduced tubes, containing bits of 

 fponge into the ftomach of a crow. In four hours 

 the tubes were vomited up, and the fponges, being 

 prefled, yielded thirty-feven grains of gaftric liquor, 

 which was frothy, of a turbid yellow colour, had a 

 tafte intermediate between bitter and fait, and being 



