330 EPITHELIAL AND ENDOTHELIAL TISSUE. 



Salivary and mucous corpuscles arise by this same slow action 

 from the contents of the epithelia. The investment of the 

 cement-substance, being partly or totally emptied and perforated 

 at one end, gives the appearance of a " goblet-cell." Formations 

 termed goblet-cells are met with, in numbers greatly varying 

 on all mucous surfaces ; they are very numerous in the small 

 intestine of rabbits suffering from diarrhoea, and also in the 

 mucosa of the artificially inflamed stomach of animals (Strieker 

 and Kocslakoff). 



A similar process of the formation of mucus is often observed 

 in the mucous glands of the frog's skin ; here the production of 



\ 

 FIG. 143. Mucous GLANDS FROM THE SKIN OF A FROG. 



C, connective-tissue frame, carrying medullated nerve-fibers, N, coursing between the 

 glands, S, and sending delicate ramules to the cement substance of the epithelia ; K, elon- 

 gated cuboidal epithelia, partly transformed into M, the mucous globules ; L, the central 

 caliber. Magnified 400 diameters. 



mucus from the epithelia of the gland is diagrammatically plain. 

 (See Fig. 143.) 



A variety of mucous secretion is that of the stomachic juice, 

 of the bile, and the semen. The acidity of the stomachic juice 

 is unquestionably due to a peculiar chemical action of the living 

 matter of the epithelia, for the blood is always alkaline. The 

 bile is a product of the liver-epithelia, each of which is a labor- 



