ALIMENTARY CANAL AND ITS APPENDAGES 407 



deeper portions of the glands are lined by a layer of shorter and 

 somewhat cuboidal cells, the central or chief cells. In s|>eciinens 

 taken from a healthy animal killed dur- 

 ing digestion these cells arc large and do 

 not stain .deeply with carmine. Similar 

 specimens taken from an animal an hour 

 or two after a good meal has been swal- 

 lowed show the chief cells shrunken and 

 staining more deeply. They, thus, store 

 up during rest a material which they get 



i r L xu ^ , FIG. 130..' 



rid of when the gastric juice is being throu K h ti 



corrr>torl membrane, ixTix-iulicular to 



QCLICtCU. f 



its surface, magnified about 



In the pyloric end of the stomach only 25 diameters, a, a simple 



,,..,,,.,. gastric gland ;b, a com pound 



the chief cells line the glands, but else- gastric gland c. & K iand con- 



where there is found outside of them, in 



most of the glands, an incomplete layer nective tissue. 



of larger oval cells (d, Fig. 130). The glands frequently branch 



at their deeper ends. 



The Pylorus. If the stomach be opened it is seen that the 

 mucous membrane projects in a fold around the pyloric orifice and 

 narrows it. This is due to a thick ring of the circular muscular 

 layer there developed, and forming around the orifice a sphincter 

 muscle, which, by its contraction, keeps the passage to the small 

 intestine closed except when portions of food are to be passed on 

 from the stomach to succeeding divisions of the alimentary canal. 



Since the cardiac end of the stomach lies immediately l>cneath 

 the diaphragm, which has the heart on its upper side, its over- 

 distension, due to indigestion or flatulence, may impede the action 

 of the thoracic organs, and cause feelings of oppression in the 

 chest, or palpitation of the heart. 



The Small Intestine (Fig. 136), commencing at the pylorus, ends, 

 after many windings, in the large intestine. It is about six metere 

 (twenty feet) long, and about five centimeters (two inches) wide 

 at its gastric end, narrowing to about two-thirds of that width at 

 its lower portion. Externally there are no lines of subdivision on 

 the small intestine, but anatomists arbitrarily describe it as con- 

 sisting of three parts; the first twelve inches being the duodenum, 

 D, the succeeding two-fifths of the remainder the jejunum, J, and 

 the rest the ileum, I. 



