MONOTREMATA. 
i fl WT | 
\ "AN |W 
yA 
Mammary gland, Ornithorhynchus, nearly arrived at 
full size. ( Mechel. ) 
i} 
‘ 
403 
Geoffroy has argued (Annales des Sciences 
Nat. ix. 1826, p.457) that the subcutaneous 
abdominal glands considered by Meckel as 
mammary, possess none of the characters of a 
true mammary gland ; he states that he exa- 
mined them with the greatest attention, com- 
paring them with the human mammary glands, 
and especially with those of Marsupial animals, 
and that they were of a totally different texture, 
consisting of a vast number of cacums placed 
side by side, all directed to the same point of 
the skin, where only two excretory orifices were 
to be perceived, and these orifices so small 
that the head of the smallest pin could not be 
made to enter them. That above all there was 
no trace of nipples; that in the specimen 
\\\ examined by him, which had the size and ap- 
} pearance of an adult female, the apparatus in 
question was not more than a fourth part the 
size of that observed by Meckel. But a mam- 
mary gland, Professor Geoffroy observes, when 
arrived at its full development, occasions an 
enlargement of all its constituent parts, the 
nipple acquiring additional bulk even before 
lactation commences, and that there was no 
appearance of this kind in the Ornitho- 
rhynchus. He considers, therefore, these ab- 
dominal glands as analogous to those which 
are situated along the flanks « Salamanders, 
and still more to the odoriferous glandular ap- 
paratus which is concentrated at the sides of 
the abdomen in the Shrews. 
In the absence of direct testimony of the 
nature of the secretion of the abdominal sub- 
cutaneous glands of the female Ornithorhyn- 
chus, the next obvious step was to test their 
disputed nature and office by an examination 
of their periods of increase and functional 
activity, as compared with those of the ovaria. 
If these glands had been analogous to the scent- 
glands of the flanks in the Shrews, and if their 
secretion had been destined to attract the male 
to the sexual intercourse, as suggested by Pro- 
fessor Geoffroy, their development ought to 
) have proceeded pari passu with that of the ova- 
ria, and the enlargement of both organs ought 
to have simultaneously reached its maximum. 
But in specimens in which the ovisacs were 
enlarged so as to indicate the ova to be ripe 
for development, I found* that the abdo- 
minal glands had madea comparatively slight 
progress to their full size (fig. 199). This 
pv ca NAFTA 
a 
Mammary gland, Ornithorhynchus, natural size at 
non-breeding season. 
(Owen, Phil. Trans. 1832.) 
* Philos. Trans. 1832, p. 525. 
2D2 
