The special-pleaders who formed the Council of the late Board of Health argued that, “as there exists an obvious harmony between our physical and social constitutions, the necessity of intercourse between all the members of the human family is one of the final necessities of our race” (“Report on the Quarantine Laws,” Board of Health, p. 64); in other words, that “the diseases supposed to be contagious by our predecessors, _cannot be contagious_, because such a supposition is at variance with _a theory (of their own invention)_ that there exists a necessity of intercourse between all the members of the human family;” and therefore all quarantine laws ought to be abolished. But are not small-pox, measles, scarlatina, hooping-cough contagious? And as regards “the necessity of intercourse between all the members of the human family,” were we to consult the Chinese, the Hindoo, the Peruvian, the Mexican, the Caffre, the Negro, the Turk, the Morocene, they would unhesitatingly tell you that such an intercourse is sure to end in their destruction. Under a Trajan or an Alexander, an Antonine, or even an Augustus, the world no doubt was benefited by an universal intercourse between all the members of the human family _then known_, and such an intercourse was highly beneficial to humanity; but the kind of intercourse established by the Clives and Pizarros is of a very different nature from that of Alexander and Trajan. Civilization is the direct result of artificial wants, the gratification of which can alone be met by a free and unrestricted commerce. By violence an empire may be overthrown, and by rapacity its inhabitants may be deprived, not only of their land and property, but even of their natural rights as men, as in India under the administration of England; but all these crusades have no reference whatever to an ameliorating of the condition of mankind; they simply form episodes in the history of the human race, respecting which historians take extremely different views. The conquests of Mexico and Peru and India form episodes in the respective histories of Spain and Britain by no means flattering to the character of these nations. CHAPTER VII. ON THE DECOMPOSITION AND METAMORPHOSIS OF ANIMAL BEINGS, AND ON THE INFLUENCE THEY EXERCISE OVER THE SOIL AS A HABITAT FOR MAN.