The number of deaths caused by small-pox in the epidemic of the years 1870–2 was greatly increased by the extremely virulent character of the disease. Of course one cannot estimate the number of deaths caused by small-pox among the civil inhabitants from the number of reported cases of the disease, since the reports sent in were always very incomplete. We know that the mortality of small-pox depends very much upon vaccination; vaccinated persons succumb far less frequently to the disease than unvaccinated persons. This fact explains why among the German field-soldiers, who were constantly subjected to hardships and privations of all kinds, only 5·75 per cent of the patients died, whereas of the French prisoners some 13·85 per cent died. The mortality among the civil inhabitants of Germany was also very high; this was chiefly due to the fact that severe forms of the disease, particularly hemorrhagic small-pox, were of frequent occurrence. As authority for this we can only refer to these reports of the hospitals; but since small children, amongst whom the mortality of small-pox is very high, are less represented in them, and, on the other hand, since mild cases among adults can more readily be withdrawn from hospital treatment, one cannot accept without qualification the experience of the hospitals. According to Wunderlich, of 681 patients treated in the Leipzig hospital between the year 1852 and July 1870, only 29 (4·2 per cent) died, whereas in the years 1870–1, of 1,727 patients treated, 253 (14·7 per cent) died. In Breslau, whereas in former epidemics an average of seven per cent of the patients died, in the epidemic of the years 1871–2 no less than 13·4 per cent died. Guttstadt also states that the mortality in the Berlin hospitals was fifteen per cent, whereas the number of deaths caused by the disease in former years was much smaller. We have seen above that 21·7 per cent of the patients taken to the Hôtel-Dieu in Lyons died. It is unnecessary to adduce further statistics; all contemporary observers agreed that the epidemic involved an extremely severe and virulent form of the disease, and that this same virulence characterized the disease wherever it made its appearance.