38 



TISSUE OF GLANDS. 



[sect. 21. 



#^N 



Some vesicles from the thyroid of a child ; magnified 

 250 times, a. Connecting fcsue between them. 6."llem- 

 braue of the vesicles, c. Epithelium of the same. 



Fig. 12. 



3. Open, roundish, or elongated glandular vesicles, with a mem- 

 Fig. 11. brana propria and an epi- 



thelium. In the racemose 

 glands (fig. 12). 



4. Open glandular tubes, 

 toith a membrana propria, 

 or a fibrous coat and an 

 epithelium. Tubular glands 



(%• 1 3)- 



To these elements (except 

 in the glands mentioned 

 under 2, which discharge 

 their contents by the occa- 

 sional bursting of their fol- 

 licles, or simply allow them 

 to transude, and the most 

 simple tubular glands) are 

 superadded special excretory 

 ducts, which, often variously ramifying, either pass directly into the 

 glandular vesicles and tubes, or, as in 

 the liver, gradually transform them- 

 selves into the secerning cell network. 

 These ducts at first very much re- 

 semble the secerning parts in struc- 

 ture, but always possess epithelial 

 cells which are destitute of the speci- 

 fic contents of the proper gland-cells, 

 and generally present a different form 

 from the latter. Thick excretory ducts 

 consist of a fibrous coat and an epi- 

 thelium, often, also, of a muscular 

 layer. And, towards their termin- 

 ation, a fibrous, muscular, and a 

 mucous coat very frequently appear 

 as special structures. 



But little is yet known concern- 

 ing the chemical constitution of 



glands. The gland-cells, as the most important structures, agree, 

 in this respect, also, with the epithelial structures, except that 

 they frequently contain special matters in their interior, such as 

 fat, the constituent of the bile, urine, gastric juice, mucus, etc., 

 and by this means acquire a specific character. 



Two smallest pulmonary lobules, a a. 

 With the air-cells (6 b), and the finest bron 

 chial twigs (c c), on which, likewise, other 

 air-cells are seated. From a newlv-born 

 child ; magnified twenty-five times. "Serai- 

 diagrammatical. 



