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 STEPHEN HALES 449

told him of the great benefit derived from ventilators installed in transport-ships to Nova Scotia; the deaths in ventilated to those in non-ventilated ships being as one to twelve. Through soliciting the interest of the French man of science dn Hamel de Monceau, Hales contrived to have his ventilators installed in certain prisons in France where English prisoners were confined. He jokingly said that he hoped that he would not be accused of assisting the enemy. The reverend sanitarian closes his paper with these words :

Thej little consider that it is the high degree of putrefaction (that most ■abtle dissolvent in nature) which a foul air acquires in long stagnating which gives it that pestilential quality which is caUed the gaol-distemper, and a very small quantity or even vapour of this highly attenuated venom like the infec- tion or inoculation for smallpox soon spreads its deadly infection. Ought not men therefore ... to use their utmost endeavours to shun this pestilential destroyer by which millions of mankind have perished in ships.

Now this is a somewhat remarkable paragraph to have been written in 1755. It undoubtedly refers to typhus fever, known under all the following names: putrid fever, pestilential fever, ship fever, emigrant fever, hospital fever, and gaol fever. It was, for it is happily now quickly disappearing, the fever of bad sanitation, the scourge of un- washed, ill-fed, badly housed, neglected specimens of humanity. Even now its precise cause, whether coccus, bacillus or other parasite, is not known. The very latest suggestion is that it is an ultra-microscopical virus transmitted by some insect that infests persons of unclean skins. But the very fact that to-day we have not isolated the virus is a sufiS- cient proof of its excessively elusive nature — ^a very attenuated poison indeed, as Hales says. Of course Hales did not know it as typhus fever : typhus, typhoid and relapsing fever were all confused until Sir William Jenner about 1850 clearly distinguished between the first two. With the rise of bacteriology, the microorganic origins of the last two have been established; the true cause of typhus has still to be dis- covered. While pathologists are still struggling over the precise cause of this fever, the practical sanitarians have almost banished it from Great Britain. Better feeding, more facilities for personal cleanliness, and above all a clearer appreciation of what ventilation means have co- operated in abolishing this horrid scourge ; but let us never forget that the initial, intelligent stages of the war against it were undertaken by Stephen Hales.

Amongst other analyses Hales made was the analysis of the expired air. He evidently regarded death in explosions in mines and of the animals in the '^grotto di cani'' as being due to the same poisonous gas.

Besides attacking and solving the problem of ventilating such places as most urgently needed it, Hales devised a method whereby a person could enter an irrespirable atmosphere and continue to breathe,

VOL. III. — ^31.

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