762 



ANATOMY OE VERTEBRATES. 



598 



Mammary gland, Ornithorhynchus ; nat. size at non-breeding 

 season, lxxvi'. 



599 



making 



cormm 



Terminal ducts, and lobe of mammary gland, injected 

 twice nat. size, lxxvi'. 



and not the cellular mem- 

 brane was filled, were 

 dried, and various sec- 

 tions were submitted to 

 microscopical examina- 

 tion. At the greater ex- 

 tremity they are minutely 

 cellular, the cells com- 

 municating with ducts 

 elongating as the lobule 

 grows narrower, dilating, 

 and terminating in a 

 larger central canal, or 

 receptacle, from which 

 the excretory duct is con- 

 tinued. On 

 section of the 

 through the middle of 

 the areola the ducts are 

 seen to converge to the 

 external surface, but 

 there is no inverted or 

 concealed nipple at this 

 part, as in the Kangaroo. 

 Fig. 599 gives a magni- 

 fied view of this section, 

 with the section of one 

 of the dried and injected 

 lobules. On the first an- 

 nouncement, by Mec- 

 kel, of the existence 

 of abdominal glands of 

 the size and structure 

 shown in fig. 596, it was 

 objected, that they did 

 not possess the charac- 

 ters of a true mammary 

 gland, and that they re- 

 sembled rather the clus- 

 ters of elongated follicles 

 situated on the flanks of 

 Salamanders, and still 

 more to the odoriferous 



