[40] It is not denied here that he made five experiments on human beings. See Part IV. chap. ii. Furthermore, Sanarelli was able to show the preventive value of the serum. At the end of February 1898, yellow fever broke out in the jail at San Carlos:-- "La première victime fut un condamné, qui vivait avec tous les autres dans une salle oû les conditions hygiéniques étaient assez mauvaises. Le lendemain, la sentinelle, qui était en rapport continuel avec la salle des condamnés, tombait malade. Quelques jours après, un autre condamné suivait le sort du premier, et bientôt un quatrième cas, mortel aussi, finit par signaler la prison comme un nouveau foyer d'infection qui venait s'allumer au centre d'un quartier de la ville encore resté indemne. "Si on avait abandonné la chose à elle-même, on aurait vu se produire le même spectacle qu'avaient fourni, dans les conditions identiques, pendant les dernières épidémies, les prisons de Rio-Claro, de Limeira, et d'autres villes de l'État de Saint-Paul." Every prisoner, except one who had already had the fever, was therefore given the preventive treatment. At once the outbreak stopped; no more cases occurred, though only a weak serum was used, though the state of the prison and its occupants was unhealthy, though the fever, two months later, was still raging round the prison, in the town. In October 1900, the United States Commission on Yellow Fever published a preliminary report on 11 cases of mosquito-inoculation. Of these, the majority gave a negative result, and were found susceptible to infection, at a later date, from the blood of a yellow-fever patient. Two gave a positive result. In the course of these experiments, Dr. Lazear, a member of the Commission, died of the disease. In February 1901, and again in July, the Commission published further reports, emphasising the fact that the mosquito conveys the disease, and denying that the disease can be conveyed in clothing, bedding, and so forth:-- "Our observations appear to demonstrate that the parasite of this disease must undergo a definite cycle of development in the body of the mosquito before the latter is capable of conveying infection. This period would seem to be not less than twelve days. "We also consider the question of house infection, and are able to show that this infection is due to the presence of mosquitoes that have previously bitten yellow-fever patients; and that the danger of contracting the disease may be avoided in the case of non-immune individuals who sleep in this building, by the use of a wire screen. "We also demonstrate, by observations made at this camp (Fort Lazear), that clothes and bedding contaminated by contact with yellow-fever cases, or by the excreta of these cases, is absolutely without effect in conveying the disease."