Germs, dust, and disease : two chapters in our life history / by Andrew Smart.

Date:
[1882]
Catalogue details

Licence: Public Domain Mark

Credit: Germs, dust, and disease : two chapters in our life history / by Andrew Smart. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    a bright ray, for example, from the electric light, or lime light, is thrown across a darkened room. When the flame of a s]!)irit-lamp is then placed under this ray it gives the appearance of smoke passing through it, but there is no smoke from the spirit- lamp, and the black space is produced by the heat of the lamp burn- ing the particles floating in the luminous beam, and for the time being rendering that part void, or empty of particles. The black spot thus produced is said in scientific phrase to be optically empty. The experiment may be turned to practical and really useful account, by showing us that these particles may be prevented from entering the lungs. Thus, a handful of cotton is placed against the mouth and nostrils, and a full breath inhaled through it, which is easily done. The cotton is now removed, and the air in the lungs made to pass through a glass tube into the luminous ray, when a dark smoke-like space is seen, as in the previous experi- ment with the spirit-lamp. This shows that the air is filtered of its particles by passing through the cotton. DISTINCTIVE CHAEACTERS OF INFECTIOUS DISEASES. Accepting, as we do, the theory that each case of infectious disease originates in the reception of a distinctly specific, pre- existing poison, and that it in turn becomes self-propagat- ing, we now go on to speak a little in detail of each of these zymotics. There are some features which are common to the whole group. They all, for example, begin with a period of whal is called dormancy or latency or incubation, during which the poison is actively developing. But the duration of this period differs in each case. That of smallpox is twelve days; typhus fever, eight to fourteen days; typhoid fever, fourteen to twenty-one days; scarlet fever, three to six days; measles, about four days. These diff'erences in the length of the incubation period being probably due in each case to the amount and strength of the poison received. At the termination of this period, the sickness is said to begin, although its distinctive character may not appear for some days longer. These fevers