522 
MR. OWEN ON THE MAMMARY GLANDS 
plied in his Archie fur Anatomie und Physiologie, B. x. p. 23 ; where, after 
combating the arguments drawn by Professor Geoffroy from the supposed 
follicular structure of the glands and the absence of a nipple, he particularly 
urges the great difference of size which the glands presented in the two 
females examined, and also their total absence in the male, — both which cir- 
cumstances he considers as strongly corroborative of his original opinion. 
In the same work (B. x. p. 568,) Professor V. Baer, in support of the opinion 
of Meckel, adduces the example of a mammary gland analogous in simpli- 
city of structure to that of the Ornithorhynchus, viz. in the Cetacea, where its 
function has never been questioned. But as no additional particulars relative 
to the structure of the glands in the Ornithorhynchus have arisen out of this 
discussion, I shall not dwell further on the arguments used by these celebrated 
anatomists, but proceed to give the results of my own investigations relative 
to this subject. 
In five apparently adult and full-grown Ornithorhynchi examined by me, 
the mammary glands presented as many different degrees of development. In 
one of the specimens they were even larger than in that dissected by Meckel, 
measuring in length respectively five inches and a half, in breadth two inches, 
and in thickness from four to five lines. In another specimen they did not 
exceed one inch and a half in length, and were only five lines in breadth, and 
half a line in thickness. In the remainder the mammary glands were of 
intermediate sizes to the two above mentioned. 
In each specimen the gland was composed of from one hundred and fifty to 
two hundred elongated subcylindrical lobes, disposed in an oblong flattened 
mass, and converging to a small oval areola in the abdominal integument, 
which areola is situated between three and four inches anterior to the cloaca, 
and about one inch from the mesial line. The lobes in the smaller glands pre- 
serve the same breadth to near their points of insertion, but in the larger ones 
they are broadest at the free extremity, measuring three or four lines across, 
and become narrower to about one third from the point of insertion, where they 
end in slender ducts. The lobes are almost all situated to the outer side of 
the areola, and consequently converge towards the mesial line of the body. 
Between the glands and the integument the panniculus carnosus is inter- 
posed, closely adhering to the latter, but connected with the glands by loose 
