2b8 



OEIGIN OF THE GLANDS. 



Fig. 276. First appearance of the parotid 

 gland in a human embryo of the seventh 

 week ; magnified twice. 



wmcn consists of a firmer granular mass, appears white, and in 



the form of an ele- 

 gant and numerously 

 branched tree. The 

 leaf-like ends now 

 undergo transform- 

 ation into blind vesi- 

 cles, whilst thebranch- 

 es and twigs of the 

 tree become hollow, 

 and unite them selves to 

 the excretory duct (fig. 

 277). The blood- 

 vessels are seen enter- 

 ing the blastema in the 

 shape of dark ramifica- 

 tions (fig. 2/7), but of 

 much smaller diame- 

 ters than those of the 

 ramified glandular 

 canal. The finest ele- 

 ments of the secreting 

 follicles do not consist 

 properly of cells ; in 

 the liver, for example 

 (fig. 278), they are ex- 

 tremely soft, roundish, 

 granular corpuscles, 

 which give to the larger 

 lobules (A) a racemi- 

 form appearance. It 

 is betwixt these major 

 divisions or lobules 

 that the blood-vessels 

 make their entrance 

 (fig. 278, B, a, a\ 

 none ever penetrating 

 betwixt the finest ele- 

 ments of all. 



Fig. 277. Lobules of the parotid gland 

 with the excretory ducts from the embryo of a 

 sheep four inches long, magnified eight times. 

 After Muller. 



