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.

    22/310 (page 24)
    resistant to heat, cold and drying, and therefore enable them to survive for long periods under conditions which would be fatal to ordinary bacteria and necessitate the employment of special measures for their destruction. Examples of spore bearing bacteria are those of anthrax, tetanus (lockjaw) and gas gangrene. Parasites are more highly developed structures, and vary greatly in size and shape; they include the malaria parasites, amoebz of dysentery, spirochetes of syphilis, and also certain worms which cause such diseases as schistosomiasis and ankylostomiasis. All germs, like other plants and animals, are susceptible to environment and require food and suitable conditions of temperature and moisture for their growth and reproduction. They breed true to stock, 7.e. each species remains distinct ; a typhoid germ will only produce typhoid germs and malaria parasites will only produce other malaria parasites. There are a very great number of different kinds of germs and many of them are harmless, while many work for the good of mankind by carrying out processes of nature such as nitrification of the soil to produce food for plants, ripening of cheese, raising of dough in bread, and even certain digestive processes in the human intestines. The pathogenic or harmful germs are those which are capable of producing disease in man or animals under ordinary con- ditions. On getting into the body they destroy the tissues directly or by producing poisons, and thé effect of such germs depends on their numbers and virulence and the susceptibility of their victim. Three factors are necessary for the spread of communicable disease. There must be a sowrce or reservoir from which the germs come, a voule or routes by which they travel, and a destination in the body of a susceptible person. These three factors form the “‘ link-cycle ”’ of infection, and all preventive measures must be directed towards breaking these links. HOMAN CASES CONTACTS CONVALESCENTS CARRAERS. ANIMALS SUSCEPTIBLE victim. ANIMALS ©