DIFFERENT FORMS OF GLANDULAR STRUCTURE. 



397 



bud or diverticulum of the intestinal tube, which is the first condition 

 of the hepatic duct, and into which they discharge themselves (Fig. 

 108). So, again, the Pancreas first presents itself in the condition of 



Fig. 109. 



Fig. 110. 



Rudimentary Pancreas from Cod : a, 

 pyloric extremity of stomach ; b, intes- 

 tine. 



Mammary Gland of Ornithorhyncus. 



a group of prolonged follicles, or caeca, clustered round the commence- 

 ment of the intestinal tube ; and this is its permanent condition in many 

 Fishes (Fig. 109). And the Mammary Gland possesses an equally 

 simple structure in the lowest of all the Mammalia (to which group it is 

 restricted) ; namely, in the Ornithorhyncus (Fig. 110). 



717. The next grade of complexity is seen, where a cluster of the 

 ultimate follicles open into one common duct, which discharges their 

 product by a single outlet ; a single gland often containing a number of 

 such clusters, and having, therefore, several excretory ducts. A good 

 example of such a condition, in which the clusters remain isolated 

 from one another, is seen in the Meibomian glands of the eyelid 

 (Fig. Ill) ; each of which consists of a double row of follicles, set upon 

 a long straight duct, that receives the products of their secreting action 



Fig. 111. 



Fig. 112. 



i 



Meibomian glands of upper lid of 

 new-born infant. 



Portion of Cowper's gland from Hedgehog; the 

 follicles distended with air. 



and pours them out upon the edge of the eyelid. And of the more 

 complex form, in which a number of such clusters are bound together 



