Ill 
contradicting it, another passage from Milton, when he speaks 
of the 
“ Smile that from reason flows, 
To brute denied.” 
I have not thought it worth while to allude to some interest- 
ing remarks which this writer makes as to the moral attributes 
of dogs. Any one who has occupied himself with the tuition 
of these animals knows perfectly well that the “ moral sense 33 
of a dog is nothing more than the instinctive association of 
certain actions with personal inconvenience. 
With reference to the application of this double system of 
physical and mental gradation to the human family, I will 
premise that the evidence which we possess concerning the 
physiological diversities of mankind does not point to the 
conclusion that these diversities ever amount to differences of 
species. Naturalists have not yet decided what species is as 
regards the lower animals, and perhaps the lower animals 
themselves are the best judges of the matter. The test which 
has been received with most favour is hybridity, and this test 
has been applied to man. As one of the results of the observa- 
tions which have been made in this direction, it has been 
asserted that the hybrids of the Negro and Caucasian are not 
indefinitely fertile inter se. Granting this fact, what does it 
prove ? Simply that the constitutional modifications which 
adapt mankind for a residence in a tropical climate, and those 
which suit him for a temperate one, do not readily co-exist 
in the same individual. It is generally allowed that man's 
physical organization is subject to considerable variation 
under the influence of the circumstances in which he is 
placed, and that the tendency of such influence is to adapt 
him to those circumstances. The Negro has existed for 
generations under circumstances widely different from those 
which have modified the physique of the Caucasian ; is 
it, then, matter for wonderment that the Negro- Caucasian 
hybrid should inherit an organization disqualifying him for 
existence either under one set of conditions or the other ? — a 
compound, anomalous organization containing within itself 
the germs of weakness and decay ? As yet, however, the 
evidence bearing on the sterility of these hybrids is incon- 
clusive, and it is aj^urd to compare the questionable sterility of 
mulattoes with the invariable sterility of mules and other 
brute hybrids. Professor Carl Vogt, in his Lectures ' on Man, 
has endeavoured to prove that the anatomical differences 
between the Negro and the Caucasian are as great as those 
which separate * two kinds of cebus usually admitted to form 
* Lectures on Man , p. 211. 
