Fig. 202. 



406 



apparatus in the Mo- 

 notrematous quadru- 

 peds must be classed 

 with the accessory or- 

 gans of generation in 

 tlie same category with 

 the antlers of Deer, the 

 spurs of the Cock, the 

 claspers of the Shark, 

 and other peculiar 

 characteristics of the 

 male sex. It has been 

 already shown, in the 

 description of the 

 young Ornithorhyn- 

 chus, that the external 

 parts of the apparatus 

 are not so developed 

 as to distinguish the 

 sex at that immature 

 period ; a small spur, 

 concealed in a cavity 

 or socket of the inte- 

 gument covering the 

 heel, the bottom of 

 which closely adheres 

 to the accessory tarsal 

 ossicle, exists in both 

 sexes; a magnified 

 view of the part in the 

 young female is given 

 at fig. 197. As the 

 young animal advances Crural gland and spur, 

 to maturity the cutane- male Ornithorhynchus. 

 ous socket increases in ( Mechel.) 



width and depth in the female, but without 

 any corresponding growth of the rudimentary 

 spur, of which in aged female Ornithorhynchi 

 sometimes no trace remains. In the male 

 Ornithorhynchus the tarsal spur soon begins to 

 rise above the socket, and finally attains a 

 length of ten lines with a basal breadth of 

 five lines, apparently everting the tegumentary 

 socket in the progress of its growth. The spur 

 (Jig. 173, K.,e; Jig. 202, e} consists of a firm 

 semitransparent horn-like substance: it is coni- 

 cal, slightly bent, and terminated by a sharp 

 point ; its base is expanded, and notched at 

 the margin for the implantation of the ligaments 

 which connect the spur with the accessory flat 

 tarsal bone (os basilare, Meckel,) (Jig. 173, K, 

 d; fig. 202, d.) The base of the spur is co- 

 vered by a thin vascular integument. The 

 spur is traversed bv a canal which commences 

 at the centre of the base and terminates by 

 a fine longitudinal slit, about one line distant 

 from the point, closely resembling in this 

 respect the canal that traverses the poison 

 fang of the venomous snake.* Like that canal 

 also the spur of the male Monotreme is sub- 

 servient to the transmission into the wounds it 

 may inflict of the secretion of a peculiar gland. 

 This gland (, Jig. 202) is situated in the 

 Ornithorhynchus at the back part of the thigh, 

 between the femur and the long process from 

 the head of the fibula, covered by the inlegu- 



MONOTREMATA. 



* De Blainville in Balletin 

 jnathique, 1817. 



tie la Socictc Philo- 



ment and the cutaneous muscle. It is of a 

 triangular or reniform figure, convex above, 

 concave below, or towards the leg; from twelve 

 to fourteen lines in length, seven or eight lines 

 broad, and three or four lines thick, with a 

 smooth exterior, invested by a thin capsule, 

 on the removal of which the gland may easily 

 be divided into a number of small lobes. Its 

 intimate structure, as displayed by a successful 

 injection of mercury, is minutely cellular, like 

 that of the glandula Harder! of the hare or 

 goose, but with the ultimate secerning cells 

 more minute ; the excretory duct is continued 

 from the concave side of the gland, and small 

 clusters of vesicles are developed from parts 

 of its expanded commencement.* The duct, 

 (Jig. 180, L,) which is about a line in width 

 and with pretty strong tunics, descends straight 

 down the back of the leg, covered by the 

 flexor muscles and posterior tibial nerve, to 

 the posterior part of the tarsus, where it sud- 

 denly expands into a vesicle (b, fig. 202) 

 about three lines in diameter ; the vesicle is 

 applied to the base of the spur, and a minute 

 duct (c, fig. 202) is continued from it into the 

 canal which traverses the spur. 



The tarsal perforated spur and its glandular 

 apparatus are both relatively smaller in the 

 male Echidna than in the Ornithorhynchus. 

 The gland is situated lower down, in the 

 popliteal region, between the insertions of the 

 deep-seated fasciculi of the adductor femoris 

 and the origins of the gastrocnemius ; it is of 

 subspherical form, about the size of a pea, 

 with a smooth exterior; the excretory duct, 

 wide at the commencement, soon contracts into 

 a filamentary canal, which again enlarges to 

 form a small reservoir for the secretion just 

 above the base of the spur. 



The true nature and use of this apparatus 

 has not yet been determined. Its close analogy 

 with the poison apparatus in other animals 

 obviously suggests the idea of a corresponding 

 function, but no well authenticated case of 

 symptoms of poisoning consequent upon a 

 wound inflicted by the spur has been recorded. 

 It seems on the contrary that the Ornithorhyn- 

 chus possesses not the instinct of availing itself 

 of a weapon so formidable, as upon this theory 

 the spur must be, when attacked or annoyed. 

 Mr. George Bennett tried the following experi- 

 ment with a full grown wounded but lively 

 male Ornithorhynchus : " I commenced by 

 placing my hands in such a manner, when 

 seizing the animal, as to enable it, from the 

 direction of its spurs, to use them with effect; 

 the result was that the animal made strenuous 

 efforts to escape, and in these efforts scratched 

 my hands a little with the hind claws, and 

 even, in consequence of the position in which 

 I held it, with the spur also. But although 

 seized so roughly, it neither darted the spur 

 into my hand nor did it even make an attempt 

 so to do. As, however, it had been stated 

 that the creature throws itself on the back when 

 it uses this weapon, (a circumstance not very 



* Miiller, DC Glaiidularum pcnit. Struct. i>. 43, 

 tab. ii. Ik'. 10. 



