In his research, the author has referred to the original colonial accounts of epidemics; the bibliography of these old records is one of the most valuable parts of the book. He ranks malaria, dysentery, and respiratory diseases as the most destructive, from a social and economic viewpoint, of the plagues that visited the colonists. He believes that smallpox, yellow fever, and diphtheria have been overrated as hindrances to colonial development. There is evidence, however, supporting a difference of opinion on the latter statement; for example, in the chapter on smallpox the author says, "A recent medical history estimates that the introduction of smallpox into Mexico in 1519 wiped out three and one-half million Indians. What was true of South and Central America held good for North America as well." In the same chapter he says, "An epidemic in Annapolis, Maryland, during this same winter of 1756-1757 delayed the convening of