IMPROVEMENT OF AGRICULTURAL HORSES. 
633 
rule^ but the system based upon the knowledge of the effects 
of all the surrounding conditions of existence. Taking 
advantage of the changes we have observed to occur under 
natural influences^ learning by patient inquiry the methods 
of their production, and testing our conclusion by experi¬ 
ment, we arrive at last at a system, not perfect, but founded 
upon correct principles, and capable of indefinite extension. 
Although the history of the past presents few data on 
which to found a method, tliere is a lesson of patience to be 
learned from it, as there is one of hope in the present. Our 
breeders, in the absence of comprehensive and just principles 
of the science, acting according to the dictates of common 
sense, and guided by experience, have in defiance of repeated 
failures and under numerous disadvantages, done much ; still 
better, they have taught us to infer how much more may be 
done by persevering inquiry into and proper application of 
laws whose existence is hardly yet recognised. 
From time immemorial the science and practice of breed¬ 
ing have been based upon the maxim like produces like.^^ 
The idea conveyed by this dogmatic aphorism is not very 
definite. If it be intended to assert that the general charac¬ 
teristics of the parents are transmitted to the offspring under 
ordinary circumstances, nothing is added to what has always 
been perfectl}^ evident in practice; but if it be contended 
that all the qualities are under all conditions so transmitted, 
experience at once opposes itself to the proposition. The 
breeder who confines himself to the selection of parents pos¬ 
sessing all or most of the qualities he requires to cultivate 
may, up to a certain point, succeed; but beyond this there 
seems to be a peculiar tendency to revert to the original type. 
This tendency is particularly remarked when the plan of 
breeding in and in is pursued; and is corrected by selecting 
animals altogether disconnected, for the purpose of crossing. 
The breeder’s maxim is seen in this case to be open to 
objection, and a further study of the changes produced by 
various causes acting at the same time, will prove how often 
changes affected by the alterations in surrounding circum¬ 
stances lead to the transmission, in an exaggerated or a 
defective degree, of the qualities of the parents. 
Education, also, which is one of the conditions capable of 
infinite modifications, would seem almost to have the power 
of originating faculties which did not pre-exist, but which, 
when called forth, are transmitted and even exaggerated. 
But careful selection and attention to all the requisite condi¬ 
tions, and among them a continuance of the educating pro¬ 
cess, seem to be indispensable to the perpetuity of the faculty. 
XXX vi. 4:i 
