ANATOMY AND PHYSIOLOGY OF THE HORSe’s FOOT. 7 
Id man, the hand attains its most complex form, and from 
him, through a series of well-defined gradations, it reaches 
its simplest condition in the horse, in which, as remarked by 
Professor Owen,* the whole limb is a jointed ray, but every 
part is adaptively modified for special ends and reciprocal 
adjustment and interplay. In the monodactyle animal it is, 
in fact, the result of simplification from a complete ancestral 
condition of limb, in reference to the application of that 
limb to a more vigorous kind of locomotion. 
This gradation from the complex to the simple form will be 
apparent in the foregoing drawings (fig. 2) , in which we have 
the hand of Man ( 0 ), next that of the Orang ( b ), then the Spider 
Monkey (c),and afterwards the fore extremity corresponding 
to the hand of the Hyaena ( d ), Megatherium (e), Sloth (/), 
Paleotherium (g) } Hipparion (or Miocene fossil horse) (h), 
and Horse ( i ). 
It will be observed that there is a gradual consolidation or 
fusion of certain digital rays, particularly the middle bones, 
and abbreviation of others, chiefly the lateral ones, until, at 
last, we have in the horse what was the hand in man only 
represented by the middle or third finger, which constitutes 
the large, small, and hoof bones. 
The transition from the highest or most complex, to the 
lowest or simplest forms, is far from being abrupt, the depar- 
ture from the typical model proceeding only step by step, in 
concordance with the great law of unity. But, notwith- 
standing this evident chain of relationship, some discussion 
has taken place among comparative anatomists as to the 
type after which the foot of the horse (in its proper sense) is 
formed. By one party it has been asserted that it is the tri- 
dactylous type, and by another the pentadactylous. In a 
most able communication made to the Toulouse Academy of 
Science in 1868, M. Lavocat, the talented director of the 
Imperial Veterinary School of that city, demonstrates in a 
thoroughly convincing manner that the horse’s foot belongs to 
the pentadactylous type.f The process of consolidation that has 
taken place between the Palseotheric and the Equine forms, as 
shown by this excellent anatomist, who quotes from the obser- 
vations of the learned paleontologist, M. Lartet, is not only or- 
ganic, but chronological. The true Palaeotherium occupies the 
Eocene stage of geological history; the Palseotherium hip- 
poides the inferior Miocene stage; the Hippotherium the 
upper Miocene epoch; and the Hipparion the Pleiocene 
period. These are all found in the tertiary formation, but 
* ‘ Comparative Anatomy and Physiology of Vertebrates/ vol. ii, p. 306. 
f ‘ Journal des Veterinaires du Midi,’ 1868, pp. 353, 401. 
