THE ORNITHORYNCHUS PARADOXUS. 39 
of the horn. As the membranous duct approaches the 
base of the spur, it becomes very strong, as if semicartila- 
ginous tunics were superadded to it; just as it quits the 
spur to enter the sole of the foot, the duct makes a sudden 
turn, and is much contracted ; it next expands a httle, and 
this point its parietes are so thick as to give it the ap- 
pearance of a bulb or gland, an appearance which, together 
with the deep situation of the sac in the hollow of the foot, 
led M. De Blainville to consider it as the poison-gland 
itself, and which evidently has been the cause of the very 
singular errors commited relative to the anatomy of the 
spur. When this bulb is laid open, it is found to be merely 
ia continuation of the mucous canal, which has at this point 
become greatly strengthened in its parietes, and assumed 
an almost muscular appearance. In the hollow of the foot 
the -duct opens by a sudden turn into a comparatively large 
sac, surrounded and inclosed by strong ligamentous and 
tendinous parts, connected with the small bones of the foot. 
Prom this sac or bag, which in either foot contained a good 
deal of a brownish, mucous matter, arises the great duct 
leading to the poison-gland. We may now trace this duct 
either from the sac towards the gland, or vice versa. If 
the first plan be adopted, we perceive that the duct en- 
ters the central sac by a small round orifice, and next makes 
a very sudden turn to reach the superficial part of the foot, 
and is soon found almost immediately under the integu- 
inents. From this point it proceeds towards the gland, 
gradually decreasing in strength of parietes, but increasing 
in diameter until it terminates, or rather commences in the 
poison-gland itself, situated over and somewhat above the 
flip-joint and loins. Throughout its course the duct lies 
imbedded in loose cellular membrane, and beneatl^ tlie 
caudo-tibial muscle, which must be reuioved, in order to 
