1910.] CUTANEOUS SCENT-GLANDS OF RUMINANTS. 983 



account of its distensibility, for progi^ession over soft and yielding 

 ground than a foot with its component digits united by skin 

 extending forwards from the heels to the front of the hoofs and 

 restricting their separation, it is obviously less well adapted for 

 .supporting heavy weight, for speedy propulsion over hard 

 unyielding ground, and for resisting the impact of a downward 

 leap on a mountain side, on account of the liability to rupture of 

 the integument under the strain put vipon it. 



Strengthening the feet, then, has probably been one of the 

 factors, perhaps the principal factor, that has operated in favour 

 of the reduction in size or total disappearance of the interdigital 

 clefts. This theory helps to an understanding of the fact that, 

 broadly speaking, lai"ge and heavily built Ruminants have small 

 interdigital clefts or none, and that large interdigital clefts are for 

 the most part foimd only in small animals. There are several 

 marked exceptions to this, however, and no doubt other factors 

 than the one suggested have influenced the formation of the feet, 

 such as the use or uselessness of pedal scent-glands. For example, 

 iarge Ruminants are much more easily kept in view by members 

 of their own species than small ones ; or, if they live in thick bush, 

 are more easily followed by hearing as they crash away in a 

 state of panic through the vegetation. Of these and other matters, 

 however, we shall never have full knowledge until our information 

 is much more exact than it is at present with respect to the senses 

 and to the bionomics of the species concerned. 



In the light of the above-made suggestions, the following con- 

 siderations are worth bearing in mind : — 



1. Giraffes are large, heavily built animals living in open wood- 

 land country and gallop with speed over rough uneven ground. 

 The feet are compactly built and without interdigital clefts. 

 The great height of Giraftes gives them considerable range of vision, 

 enabling stragglers to keep with the rest of the herd. They can, 

 moreover, only with difficulty and delay I'each the ground with 

 their nostrils. Hence specialised pedal scent-glands would be of 

 little use to them for tracking. 



2. All the species of Bos are heavily built, mostly large animals 

 with thick legs. They live either in the open or in jungle or bush, 

 and can be followed either by sight or by the sound they make 

 passing through the foliage. The same applies to the Musk-Ox 

 and to Taurotragus. 



3. The Oryginas [Hippotragus, Oryx) are also Antelopes of lai'ge 

 or medium size and considerable weight. The interdigital cleft is 

 reduced to a glandAvitha small orifice, which is the only break in 

 the continuity of the integument of the anterior surface of the 

 pastern ; and the orifice is smaller in the larger Hipjjotragits than 

 in the smaller Oryx. 



4. In the Bubalina?, large or medium-sized Antelopes, although 

 the interdigital cleft is large and highly glandular on the fi'ont 

 feet, it is reduced to a shallow depression on the hind feet. It is 

 in the hind limbs that the galloping power principally lies ; and 



64* 



