Page:George Archdall Reid 1896 The present evolution of man.djvu/254

242 acquired traits in multicellular organisms, and therefore of the transmissibility of the effects of disease, there are certain facts, drawn from the study of disease itself, which sufficiently negative the opinion that traits acquired under such influence are transmissible. No immunity can be acquired against tuberculosis and malaria, the two most death-dealing of all diseases; or at least no immunity can be acquired against tuberculosis, and if any is acquired against malaria it is quickly lapsed, as in relapsing fever, in the intervals between the paroxysms. Experience by the individual of either of these diseases weakens rather than strengthens him against them. If the above, the Lamarkian theory, be correct, it follows, therefore, that races which have had a long and disastrous experience of tuberculosis and malaria should be less resistant than races that have had little or no experience of them. Each successive individual of the line should begin life with less resisting power than his parent began with, and should transmit less than he received to his offspring. The contrary, however, is the case, for races that have had a long and disastrous experience of tuberculosis and malaria are more resistant than races that have had little or no experience of them; thus the Englishman who migrates to the West Coast of Africa falls an easier victim to malaria than does the negro, whereas the negro who migrates to England falls an easier victim to tuberculosis than does the Englishman. In both cases, not only is the disease more readily acquired by the stranger, but, when acquired, it is much more deadly to him than to the man whose race has had an extended experience of it. In both cases, though experience of the disease by the individual rather weakens than strengthens his power of resistance to it, yet prolonged experience of the disease by the race does not result in a weakening of its resisting power, but in a conspicuous strengthening