OF THE ORNITHORHYNCHUS PARxiDOXUS. 
523 
cellular membrane. This muscle is here nearly a line in thickness ; its fibres 
are longitudinal, anti, separating, leave an elliptical space for the passage of 
the ducts of the gland to the areola. (PI. XVIII. fig. 1.) 
On the external surface of the skin the areola (when the hair with which it 
is covered has been removed.) can only be distinguished by the larger size of 
the orifices of the ducts as compared with those for the transmission of the 
hairs, and occasionally by being of a deeper colour than the surrounding inte- 
gument. The orifices of the ducts thus grouped together form an oval spot, 
which in the specimen which had the largest glands measured five lines in 
the long, and three in the short diameter. In that in which the glands exhi- 
bited the smallest size, the areola could be traced by the aid of a lens to 
nearly the same extent in the long diameter, but it was much narrower. From 
the minuteness of the orifices of the ducts in the specimens with the small 
glands, the situation of the areola can hardly be detected without previously 
dissecting the gland ; whilst in those in which the glands are fully developed, 
the practised eye readily discovers the areola on removing the hair. In none 
of the specimens was the surface on which the ducts terminated in the slight- 
est degree raised beyond the level of the surrounding integument ; the eleva- 
tion like a millet-seed in Professor Meckel’s specimen I conceive to have 
been accidental, and not essential to the structure of the part, having observed 
similar risings in the integument at different distances from the areola, but 
not in the areola itself. The orifices, moreover, appear of nearly equal sizes, 
not any of them at least being calculated to suggest the idea of its being com- 
mon to many ducts or lobules, as might be inferred from the description of 
Professor Geoffroy. (The appearance which one of the areolse presented 
under the microscope is represented at PI. XVIII. fig. 2.) On compressing the 
glands in a specimen in the Museum of the Zoological Society, where they had 
arrived at the maximum of development, there escaped from these orifices 
minute drops of a yellowish oil, which afforded neither perceptible taste nor 
smell, except such as was derived from the preserving liquor. 
Having in vain attempted to insert the smallest absorbent pipe into these 
orifices, I thrust it into the extremity of a lobule, and after a few unsuccessful 
efforts at length perceived the mercury gradually diffusing itself in minute 
globules through the parenchyma of the lobule ; and at the distance of an 
