MONOTREMATA. 



405 



Fig. 201 



Terminal ducts, and lube of mammary gland, injected, 

 twice natural sixe. 



strongly implying its fluid nature, and most 

 contrary to the mode in which odorous sub- 

 stances are excreted ; 3rd, the excretory ori- 

 fices are by no means extended over so wide a 

 space, in proportion, as in the Shrew, but col- 

 lected into a point which we know to be not 

 disproportionate to the size of the mouth of the 

 young animal, and this point is situated in a 

 part of the body convenient for the transmission 

 of a lacteal secretion from the mother to her 

 offspring. 



Compared with an ordinary mammary gland, 

 that of the Ornithorhynchus differs chiefly in 

 the absence of the nipple, and, consequently, of 

 the surrounding vascular structure necessary 

 for its erection. But the remarkable modifica- 

 tion of the mouth in the young Ornithorhynchus 

 removes much of the difficulty which previously 

 attached itself to the idea of the possibility of 

 an animal with a beak obtaining its nutriment 

 by suction. The width of the mouth in the 

 smallest observed Ornithorhynchus corres- 



ponds with the size of the mammary areola; 

 and the broad tongue, extending to the apices 

 of the broad, short, and soft jaws, with the 

 fold of integument continued across the angle 

 of the mouth, are all modifications which pre- 

 pare us to admit such a co-adaptation of the 

 mouth of the young to the mammary outlet of 

 the parent, as, with the combined actions of 

 suction in the recipient, and compression of 

 the gland in the expellent, to effect this essen- 

 tially Mammalian mode of nourishment. 



We may presume that a corresponding mo- 

 dification of the mouth of the new-born 

 animal obtains in the Echidna, since the mam- 

 mary glands in this Monotreme* correspond in 

 structure, and mode of termination of theexcre- 

 tory ducts, with those of the Ornithorhynchus, 

 As yet the secretion of the mammary glands 

 of the Echidna has not been observed; but that 

 of the Ornithorhynchus has been detected not 

 only in the stomach of the young (ante p. 401), 

 but oozing from the lacteal pores of the female, 

 and by more than one competent observer.f 

 Mr. George Bennett, describing his dissection 

 of a female Ornithorhynchus shot at Mun- 

 doona, New South Wales, on the 14th 

 of November, the day before his arrival at 

 that place, and which " had evidently just 

 produced her young," and had very large 

 mammary glands, thus records his obser- 

 vation of their secretion. " The glands were 

 very vascular on the surface, the mammary 

 artery ramifying over them in a most beautiful 

 and distinct manner. The fur still covered 

 that portion of the integument on which the 

 ducts terminated, and there was no appear- 

 ance of a projecting nipple." " How different 

 was the appearance in the recent state of this 

 mammary gland from that which I had pre- 

 viously seen at the Royal College of Sur- 

 geons, in a specimen long preserved in spirits, 

 in which I had the opportunity of witnessing 

 the injection of the ducts with mercury by my 

 friend Mr. Owen, the mercury exuding, as I 

 have seen the milk from the similar ducts, 

 upon the integuments." Zoological Trans- 

 actions, vol. i. p. 251. In a female Ornitho- 

 rhynchus, which with her two full-furred young 

 were captured alive by Mr. Bennett on the 

 28th of December, he says, " The milk that 

 could be expressed from the glands was but 

 trifling in quantity; and, in the mother of these 

 young animals, such would have been expected 

 to be the case, for they were capable of feeding 

 upon more substantial diet." Ibid. p. 254. 

 Crural gland and spur.^ This remarkable 



* See Phil. Trans. 1832, p. 537, p!. xvii., figs. 

 2 and 3. 



f Hon. Lauderdale Maule, Proc. Zool. Society, 

 part ii. p. 145. G. Bennett, Esq. ib. part i. p. 82. 

 Partii. p. 141-11. 



Hf Meckel, loc. cit. p. 54, calls this peculiar 

 sexual gland ' femoral,' observing," ne ipso no- 

 mine de functione judicium proferam, forsan re- 

 trahendam, hoc nomen a situ impono." As, how- 

 ever, the femoral position is peculiar to the Orni- 

 thorhynchus, the gland being popliteal in the Echid- 

 na, I prefer a name derived from the word ' crus,' 

 which has a more extended signification to the 

 whole hinder extremity. 



