78 ACTION OF WILD ANIMALS ON VEGETATION. 
If tlie myriads of large browsing and grazing quadrupeds 
which wander over the plains of Southern Africa and the 
slaughter of which by thousands is the source of a ferocious 
pleasure and a brutal triumph to professedly civilized hunters 
—if the herds of the American bison, which are numbered by 
hundreds of thousands, do not produce visible changes in the 
forms of terrestrial surface, they have at least an immense 
influence on the growth and distribution of vegetable life, and, 
of course, indirectly upon all the physical conditions of soil 
and climate between which and vegetation a mutual inter¬ 
dependence exists. 
The influence of wild quadrupeds upon vegetable life has 
been little studied, and not many facts bearing upon it have 
been recorded, but, so far as it is knowm, it appears to be con¬ 
servative rather than pernicious.* Few if any of them depend 
for their subsistence on vegetable products obtainable only by 
the destruction of the plant, and they seem to confine their 
consumption almost exclusively to the annual harvest of leaf 
or twig, or at least of parts of the vegetable easily reproduced. 
If there are exceptions to this rule, they are in cases where the 
numbers of the animal are so proportioned to the abundance 
of the vegetable, that there is no danger of the extermination 
of the plant from the voracity of the quadruped, or of the 
extinction of the quadruped from the scarcity of the plant. 
In diet and natural wants the bison resembles the ox, the ibex 
* Evelyn thought the depasturing of grass by cattle serviceable to its 
growth. “ The biting of cattle,” he remarks, “gives a gentle loosening to 
the roots of the herbage, and makes it to grow fine and sweet, and their 
very breath and treading as well as soil, and the comfort of their warm 
bodies, is wholesome and marvellously cherishing.”— Terra , or Philosoph¬ 
ical Discourse of Earth, p. 86. 
In a note upon this passage, Hunter observes: “ Nice farmers con¬ 
sider the lying of a beast upon the ground, for one night only, as a suffi¬ 
cient tilth for the year. The breath of graminivorous quadrupeds does 
certainly enrich the roots of grass ; a circumstance worthy of the attention 
of the philosophical farmer.”— Terra , same page. 
The “ philosophical farmer ” of the present day will not adopt these 
opinions without some qualification. 
