INSALIVAT10N. 



175 



considers them to be undeveloped mucous cells, destined to replace 

 the secreting cells when they shall have ceased to perform their 

 function and have disappeared ; while other opinions are that they 

 are a distinct type of albuminous cell, or are due to a post-mortem 

 change. Some observers claim to have demonstrated that the 

 lumen of the albuminous glands is continued as fine capillary 

 spaces between the cells of these glands, and that from these pass 

 off smaller branches which penetrate the cells themselves, and 

 that in the mucous glands these same capillaries exist only in con- 

 nection with the demilunes. If this is confirmed, it would seem 

 to be more than probable that the demilunes have distinct secre- 

 tory functions. 



The albuminous gland secretes a watery or serous fluid, which 



FIG. 98. Parotid of the rabbit, in tbe resting condition (after Heidenhain). 



contains, besides water, inorganic salts, some albumin, and may 

 also contain enzymes. The cells of this variety are small and 

 compactly fill the alveoli, leaving but little lumen (Fig. 98). 

 They contain albuminous granules which are very distinct. The 

 parotid gland represents the serous or albuminous type. 



The human submaxillary gland is a mixed type containing 

 both mucous and albuminous alveoli, the latter, however, in greater 

 number. 



It is a fact that in mucous glands some cells are found which 

 are regarded as characteristic of the albuminous type, and vice 



