230 THE ANIMAL KINGDOM. 



of three separate layers or sets of fibres,, which give it the 

 power of contraction and dilatation. It is lined with a 

 mucous membrane, smooth and velvety when distended, 

 but loose and plaited when contracted. The internal sur- 

 face is somewhat like honeycomb, with shallow cells, at the 

 bottom of which lie the minute orifices of the gastric glands. 

 We see these glands looking somewhat like villi in the 

 injected preparation, but they are essentially different both 

 in structure and office. These tubular glands produce the 

 cells containing the gastric juice which digests our food. 

 When the stomach is empty they are at rest and the 

 orifice of each is closed, but no sooner does food enter the 

 stomach than the capillaries surrounding each gland 

 become excited, and the glands commence actively secreting 

 an acid fluid, which oozes in minute drops from their open 

 mouths and mixes with the contents of the stomach. 



The pyloric opening is the passage into the duodenum ; 

 during the first part of digestion it is completely closed, 

 but as digestion progresses it relaxes more and more, suf- 

 fering even undigested portions to go through it. 



THE SKIN. 



Injected portions of the skin usually show the fibro- 

 cellular tissue called the corium, elastic, yet dense and 

 tough, beneath which lie the important sweet-glands, the 

 hair-follicles, and the papillae. The web that we see is com- 

 posed of fat- cells, blood-vessels, absorbents, and unstriated 

 muscular fibre. 



SECTION OF PALM OF THE HAND OR FOOT OF CAT DOG 



MONKEY. 



This will show the cutis above and the papillae beneath, 

 forked or trifid with loops of capillary blood-vessels. The 

 papillae are not all furnished with nerve-fibres ; many of them, 

 have merely blood-vessels for the supply of the epidermis, 

 and those which possess nerve-fibres are usually destitute of 

 blood-vessels. The sensory papillae contain a peculiar 

 " axile body," or bundle of fibrous tissue, upon which the 

 nerve-fibre terminates. 



