Army manual of hygiene and sanitation, 1934 / [War Office].

Date:
1941
Catalogue details

Licence: Public Domain Mark

Credit: Army manual of hygiene and sanitation, 1934 / [War Office]. Source: Wellcome Collection.

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    carried by any of these routes to their destination, the suscep- tible victim, they enter the body by different channels of infection. They may enter by the mouth in food, water, or dust and be swallowed or inhaled: in certain diseases they may get through the broken skin in scratches or sores, while in others they may be inserted into the blood by insects such as mosquitoes, ticks, fleas or biting flies which have previously fed on diseased men or animals. After they have invaded the body of their victim there is an incubation period before symptoms of the disease manifest themselves; during this the germs multiply and produce poisons. The length of this incubation period varies in different diseases; for example, in scarlet fever it may be as short as two days, while in typhoid fever it may extend to three weeks (see Appendix 3). Persons who have been contacts with a case of communicable disease must be kept under observation to see whether they show signs of developing the disease at the end of the incubation period ; for example, con- tacts with a case of measles should be inspected daily from the seventh to the sixteenth day after exposure to infection. A person in robust health has the power to resist the attack of germs by means of certain constituents in his body, particu- larly in his blood, which render the germs harmless or destroy them. This power of resistance is reduced by conditions such as fatigue, exposure or starvation, which lower the vitality and allow the germs to gain the upper hand and produce disease. Germs may be present in the body and have no ill-effect until a lowering of the vitality of the body enables them to overcome the normal powers of resistance. The healthy man may be protected against disease either by preventing the disease germs getting into his body or by increasing his powers of resistance so that, even if germs do gain entrance, his body is capable of overcoming and destroy- ing them, Examples of the prevention of access of germs are the use of nets against mosquitoes, the protection of food against flies by means of covers and meat safes, the purification of water supplies, the sterilization of eating and drinking utensils, and the use of rubber sheaths during sexual intercourse. The powers of resistance of the body may be increased by attention to environment, sanitation, and general bodily and mental welfare, and also by conferring immunity by means of preventive inoculation. Immunity is the power to resist disease and may be natural or acquired. Natural immunity is possessed by every one, but it varies in degree in different individuals and at different times in any one individual. Some persons have a natural immunity