34 PROF. OWEN ON THE ANATOMY OF THE INDIAN RHINOCEROS. 



callous protuberance, scarcely an inch in height and onlj' four inches across the base, 

 although the animal was nine feet in length and the same in its greatest circumference. 

 This difference indicates that the epidermal production in question varies in its pro- 

 portions in the male and female, making a sexual distinction analogous to that which 

 may be observed in the antlers of the Reindeer, the false antlers of the Giraffe, and in 

 some other Ruminants in which horns are present in both sexes'. 



Since, as Daubenton well demonstrated, and as has been amply confirmed and eluci- 

 dated by later observers, the horn of the Rhinoceros is an unvascular production, an 

 agglutination of fibres like bristles, unsupported by any osseous core, the question early 

 suggested itself to me, how the relative position of the epidermal conglomerate to the 

 eye and the end of the muzzle was preserved during the progressive growth of the head, 

 and I have carefully watched the progress of the horn in the male animal here described 

 from its first reception into the Society's Menagerie. During the whole of the period 

 of the animal's growth, the back part of the horn was that which alone exhibited natural 

 decay ; the fibres there being ragged and broken, while the new fibres were added at the 

 sides and chiefly in front. Thus the horn kept pace, as to its relative position, with 

 the progressive elongation of the jaws during the acquisition of the permanent teeth, by 

 a process analogous to that by which the adductor muscle of the oyster maintains the 

 same relative position to the hinge and outlet of the shell during the whole period of 

 the shell's growth. This partial or local decay and renovation became less conspicuous 

 after the Rhinoceros had attained its full size, and in the long and large horns of aged 

 individuals the whole circumference presents the same smooth and polished surface : 

 whence it may be concluded that when the skull, and especially the upper jaw of the 

 Rhinoceros have attained their full size, the horn receives additional matter along the 

 whole extent of the base, and increases more rapidly in length than in the immature 

 animal. 



The glandular orifices at the back part of each foot to which I have alluded, are 

 situated about three inches above the callous sole in the fore-feet and about two and a 

 half inches above the sole in the hind-feet : they are concealed from cursory observation 

 in the middle of the transverse fold that runs parallel to the interspace between the 

 carpus and metacarpus, and between the tarsus and metatarsus. The orifice is analo- 

 gous to that which opens on the fore part of the foot between the digits in the Sheep 

 and some other Ruminants. The gland itself (PI. IX. fig. 1) in the Rhinoceros is of a 

 compressed ovate figure, measuring one and a half inch in length and one inch in 

 breadth. The thickness of the glandular parietes {lb. fig. 2) varies from two to three 

 lines. These parietes consist of a compact congeries of follicles, surrounded externally 



the freezing point : it had previously exhibited no signs of disease, and had been carried about and exhibited 

 upwards of a year. 



' In the female Rhinoceros Simus the anterior horn is longer and more slender than in the male : in other 

 two-horned species I am not at present aware of any sexual distinction in these weapons. 



