SEROUS GLANDS OF THE VALLATE PAPILLAE 369 



They are more branehccl than those of the 15 cm. specimen 

 studied, this being particularly true of the terminal portions 

 of the ducts. The gland ducts frequently divide dichotomously, 

 although occasionally they resolve into three or four branches, 

 ^^onie of the glands extend down into the muscular tissue as 

 far as the transverse muscle layer, where they spread into ter- 

 minal branches. The terminal branches, as a rule, ran hori- 

 zontally, sometimes with many turns. A few, however, are so 

 situated that their secretions are emptied into the main duct 

 against its stream. The three largest glands of the papilla 

 occupy a medial position. One of these shows especially well a 

 terminal arborization similar to that seen in figure 6, as well as 

 beginning alveolar subdivision of the end masses. In the 

 shorter glands the end pieces do not show^ as yet this formation 

 of alveoli. Only two glands arise from the outer wall of the 

 papilla. Another, possibly the anlage of a mucous gland, has its 

 origin from an epithehal fold lateral to the papilla. It shows, 

 howe^'er, the same terminal enlargement as is characteristic of 

 the glands of the vallate papilla. 



One papilla of a specimen 19 cm. long was reconstructed. 

 This specimen was singular in that it presented so many gland 

 ducts to each papillae. The papilla chosen for reconstruction lies 

 on the left side near the foramen caecum. With this papilla 

 seventy-seven ducts are associated, w^hile with another papilla 

 on the left side, one hundred and four are present. In the one 

 reconstructed, tW'O glands arise from the inner w^all of the papilla, 

 the others coming from the lower border and outer wall. Some 

 ducts are 2 mm. long, others very short. The short glands are 

 characterized by short side branches and enlarged end pieces 

 (fig. 7) The breaking up of the end pieces is advanced far be- 

 yond that in younger specimens and is apparently a constricting 

 of parts to form small round, or ridge-like alveoli, the latter 

 connected by a long narrow base. Older stages demonstrate 

 that these may first sejiarate in the middle, having the ends 

 attached, and thus form anastomosing alveoli. The serous 

 glands of the vallate papillae can, therefore, in later fetal stages, 

 be considered as branched alveolar glands. Both the end 



