Dr. Hanna's book contains the results of his experience as health officer for the port of Liverpool. It consists of three parts: (1) a statistical study of 1,163 cases of small-pox, with special reference to the influence of vaccination in modifying the disease; (2) an analysis of 943 cases of small-pox (with primary vaccination) in relation to scar-area and severity of disease; (3) observations on the interaction of small-pox and vaccination. The study is an exhaustive one and the book is well illustrated with excellent photographs, well printed on good paper.
Hanna draws the conclusions from the first part that the small-pox mortality in the unvaccinated ranges from 25 to 40 per cent. and in the vaccinated is about 3 per cent.; that in the unvaccinated, those at the extremes of life, mainly children under 10 and old persons, suffer the most, the mortality of these two classes reaching as