532 
MR. OWEN ON THE MAMMARY GLANDS 
glands, which more commonly open externally by one large and wide orifice. 
The excretory orifices of the glands in the Ornithorhynchus, moreover, are not 
extended over a wide surface, but are collected into a point, in all probability, 
not disproportionate to the size of the mouth in the young animal, and these 
points are situated in parts of the body most convenient for the transmis- 
sion of a lacteal secretion from the mother to her offspring. 
Compared with an ordinary mammary gland, that of the Ornithorhynchus 
differs chiefly in being of a cellular and not of an acinous or conglomerate 
structure ; as well as in the absence of the nipple and of the surrounding 
vascular structure necessary for its erection. But the inconclusiveness of 
arguments drawn from these circumstances has been sufficiently demonstrated 
by Professors Meckel and V. Baer in the work above quoted. The question 
then arises, how the secretion of this gland, if mammary, is conveyed to the 
young ? And with respect to the absence of a nipple, Professor Geoffroy 
observes, “ C’est ainsi chez un animal dont le museau est fait de fagon que 
meme y aurait il une long tetine un tel animal serait prive de la saisir et de 
la sucer.” 
But with a form of mouth so extraordinary and unlike that of other quadru- 
peds, might we not expect some corresponding deviation from the normal 
structure in the efferent portion of the mammary apparatus ? And if a nipple 
would indeed have been useless or unavailable in this case, have we not then 
the best reason for its absence ? Unless, however, we limit nature to one 
mode only of conveying the lactiferous secretion from the parent to the off- 
spring, I apprehend the evidence afforded by the preceding details will hardly 
render tenable any other theory than that which upholds the mammary nature 
of the glands in question. 
Fortunately, an instance has already been afforded, and that too in the Mar 
supiata, of a structure superadded to the mammary gland apparently to com- 
pensate for a want of sufficient power of suction in the young animal*. So 
also in the Ornithorhynchus the strong panniculus carnosus which is every 
where interposed between the glands and the skin, may compress the glands 
* See Professor Geoffroy’s account of this apparatus in Mem. du Musdum, tom. xv. p. 48; and 
Description of the Mammary Organs of the Kangaroo, by John Morgan, Esq. Linn. Trans, vol. xvi. 
p. 61. 
