346 Effa Fnnk Muhse. 



acinus consist of a matrix in which are imbedded muscle fibers and 

 on which rests the epithelium, whatever form it may assume. The 

 number of muscle fibers increases with the size of the acinus. In 

 the smaller glands, the fibers may be few and scattered. Compared 

 with the depth of the acinus, the fibers are relatively very long, some- 

 times reaching even through half its circumference (Fig. 34). The 

 most apparent variation in the glands of the outer series is in 

 the epithelium. 



Glands with a definitely branched acinus and a common collar 

 and neck, others with both a branched acinus and collar, and the 

 neck divided for part of the way, are found occasionally. Sacs more 

 or less oval, or spherical, with a definite outpocketing or bud at one 

 side, are common. This last has also been observed in the mature 

 type. 



Two stages, a and b, have been described. 



(c) In the third stage a lumen is forming and is lined with a 

 cubical epithelium (Fig. 28). 



(d) Fig. 29 shows that in this section of a given gland, the cells 

 of the epithelium are uniformly cubical, each with a large centrally 

 placed nucleus and homogeneous cytoplasm. In an adjoining sec- 

 tion toward the center of the gland, four homogeneous cells have 

 changed into reticular cells and have projected somewhat into the 

 lumen. Part of the contents of these cells has streamed as an in- 

 definite threadlike mass into the otherwise empty lumen. Fig. 30 

 shows a somewhat similar condition, except that relative to the other 

 cells the reticular ones have enlarged more and projected further 

 into the lumen. Fig. 31 shows a gland similar to the preceding 

 ones, except that the cytoplasm of the enlarged cells has a granular 

 appearance. The nucleus of the enlarged cells of the above glands 

 has remained in contact with the base of the cell which rests upon 

 the matrix. 



(e) In a more advanced stage, the outer lower hemisphere of 

 the gland is lined with enlarged cells. These are crowded together 

 and all assume slightly polygonal foa-ms (Figs. 32-35, 50). The 

 cytoplasm of the enlarged cells may be homogeneous, reticular,, or 

 granular. All of these cells may be of one sort, or one cell may be 



