404 



MONOTREMATA. 



condition was only manifested in the females 

 with ovaria, large indeed, but without promi- 

 nent ovisacs, and in which the recent corpora 

 lutea were almost absorbed. These facts were 

 established by the dissection of five female 

 Ornithorhynchi. 



In each of these specimens the mammary 

 gland was composed of between one hun- 

 dred and two hundred elongated subcylin- 

 drical lobes, forming an oblong flattened mass, 

 and converging to a small oval areola in the 

 abdominal integument, which areola is situated 

 between three and four inches from the cloaca, 

 and about one inch from the mesial line. The 

 lobes in the fully developed glands are rounded 

 and enlarged at their free extremities, and 

 measured at that end three or four lines in 

 breadth, and became narrower to about one-third 

 from the point of insertion, where they end in 

 slender ducts. Almost all the lobes are situated 

 at the outer side of the areola, and consequently 

 converge towards the mesial line of the abdomen. 

 Between the gland and the integument the 

 panniculus carnosus (Jig. 199, ) is interposed, 

 closely adhering to the latter, but connected 

 with theglandbyloose cellularmembrane. This 

 muscle is here a line in thickness, its fibres are 

 longitudinal, and, separating, leave an elliptical 

 space for the passage of the ducts of the gland 

 to the areola. On the external surface of the 

 skin, when the hair is removed, this areola can 

 only be distinguished by the larger size of the 

 orifices of the lacteal ducts, compared with 

 those for the transmission of the hairs. 



Fig. 200. 



Mammary areola, Ornithorhynchus, natural sixe. 

 (Owen, Phil. Trans. 1832.) 



The orifices of the ducts thus grouped together 

 form an oval spot, which in the female with 

 the largest glands measured five lines in the long 

 and three in the short diameter. In none of 

 the specimens was the surface on which the 

 ducts terminated raised in the slightest degree 

 beyond the level of the surrounding integument. 



Meckel was disposed to believe that the 

 ducts terminated on a small eminence about 

 the size of a millet-seed, but did not succeed in 

 demonstrating the fact by injection of the ducts.* 



* Meckel writes : " Ductuli excretorii, maxime 

 attenuati, in glandulae medio extrorsum aperiuntur. 

 Quamvisnequesetas,neque mere uriam per ductus,et 

 per se, utmonui, angustissimos, et spiritu vini con- 



Not any of the specimens of Ornithorhyn- 

 chus examined by me have presented a 

 mammary eminence of any dimensions ; on 

 the contrary, I have succeeded in demonstrat- 

 ing the termination of the lacteal ducts on 

 the flat areolar tract. Having in vain at- 

 tempted to insert the smallest absorbent 

 pipe into the mouths of these ducts, I thrust 

 it into the extremity of one of the elongated 

 lobes, and after a few unsuccessful efforts 

 at length saw the mercury diffuse itself in mi- 

 nute globules through the parenchyma of the 

 lobe, and at a distance of an inch it had evi- 

 dently entered a central duct, down which it 

 freely ran to the areola, where it escaped exter- 

 nally from one of the minute orifices just de- 

 scribed. This process was repeated on most 

 of the lobes with similar results, the greater 

 part of them terminated by a single duct open- 

 ing exteriorly and distinct from the rest, but in 

 a few instances the ducts of two contiguous 

 lobules united into one, and in these cases the 

 mercury returned by the anastomosing duct 

 and penetrated the substance of the other lobe 

 as freely as that into which the pipe had been 

 inserted. 



Some of the lobes injected by the reflux of 

 the mercury through the duct, and of which it 

 was more certain that the glandular structure 

 and not the cellular membrane was filled, were 

 dried, and various sections were submitted to 

 microscopical examination. At the greater 

 extremity they are minutely cellular, the cells 

 communicating with each other, and elongating 

 as the lobule grows narrower, first at the centre, 

 so as to form apparently minute tortuous tubes, 

 which tend towards and terminate in a larger 

 central canal, or receptacle, from which the ex- 

 cretory duct is continued. On making a sec- 

 tion of the corium through the middle of the 

 areola the ducts are seen to converge slightly 

 to the external surface, but there is no inverted 

 or concealed nipple at this part, as in the Kan- 

 garoo. (Fig. 201 is a sketch of a magnified 

 view of this section, with the section of one of 

 the dried and injected lobules.) 



Thus, prior to and independently of any 

 direct observation of the secretion of the ab- 

 dominal glands, the anatomical facts brought 

 to bear upon their disputed function were in- 

 dubitably more favourable to the opinion of 

 the German than of the French Professor ; 

 for, 1st, the glands are confined to the female, 

 and vary in degree of development at dif- 

 ferent periods in individuals of equal size, at- 

 taining in some an enormous development ; 

 2nd, the secretion is conveyed outwardly by 

 means of numerous long and narrow ducts, 



tractos, et fluido concrete repletos,trajicere potuerira, 

 area tamen indicatur in cute. Quamvis pili hanc par- 

 tem tegant, apparet tamen, hos si abstuleris, plaga, 

 quinque circiter lineas longa, tres lata, foraminutis, 

 iis, e quibus pili egrediuntur, majoribus, nigris, 

 circiter octoginta stipata, forsan ducluum excre- 

 torium orificiis. Praeterea in hujus medio depres- 

 siuncula duarum lineatum diametri adest, pilis 

 destituta, sed eminentitmculis inaequalis, inter quas 

 prascipne una, milii granum baud aequans, reliquas 

 antecellit. Ha sine dubio papillae et ductuum ori- 

 ficia sunt." Loc. cit. p. 54. 



