398 



OF SECRETION. 



in one glandular mass, we have an illustration in the accessory glands i 

 of the genital apparatus, in several animals, which discharge their 

 secretion into the urethra by numerous outlets (Fig. 112) ; or in the 

 Mammary glands of Mammalia in general, the ultimate follicles of 

 which are clustered upon ducts that coalesce to a considerable extent 

 though continuing to form several distinct trunks even to their termi- 

 nation. Such glands may be subdivided, therefore, into glandules or 



Fig. 113. 



Lobule of Lachrymal Gland ; from foetal sheep. 



lobules, that remain entirely distinct from each other (Fig. 113). In 

 the highest form of Gland, however, all the ducts unite ; so as to form a 

 single canal, which conveys away the products of the secreting action 

 of the entire mass. This is the condition in which we find the Liver 

 to exist, in most of the higher animals ; also the Pancreas, the Parotid 

 Gland, and many others. In some of these cases, we may still sepa- 

 rate the gland into numerous distinct lobules, which are clustered upon 

 the excretory duct and its branches, like grapes upon a stalk ; in others, 

 however, the branches of the excretory duct do not confine themselves 

 to ramifying, but inosculate, so as to form a network, which passes 

 through the whole substance of the gland, and which connects together 

 its different parts, so as to render the division into lobules less distinct. 

 This seems to be the case in regard to the Liver of the higher Verte- 

 brata ( 723). 



718. Whatever degree of complexity, however, prevails in the gene- 

 ral arrangement of the elements of the Glands in higher animals, these 



Fig. 114. 



Fig. 115. 



Two follicles from the liver of Carcinus mamas (Com- 

 mon Crab), with their contained secreting cells. 



Ultimate follicles of Mammary gland with their 

 secreting cells, a, a ; b, b, the nuclei. 



elements are themselves everywhere the same ; consisting of follicles 

 that enclose the real secreting cells (Figs. 114 and 115). Now from 



