PREVENTIVE MEDICINE 199 



various diseases, and these are discussed under their respective 

 heads. Vaccine and Serum Therapy are of value in certain specific 

 instances. 



CLEANSING AND DISINFECTION 



DISINFECTION means the conversion of a place, person, or thing 

 from a potentially infective state into one which is free from 

 infection. This implies the destruction of pathogenic micro- 

 organisms and their spores. 



As micro-organisms find temporary resting places in and are 

 hidden by dirt and dust, cleansing of infective material is a neces- 

 sary combination with disinfection. 



A Disinfectant is an agent that destroys pathogenic organisms 

 and their spores. 



An Efficient Disinfectant is one which does the work required 

 of it within a reasonable limit of time. 



A Suitable Disinfectant is an efficient disinfectant that does not 

 materially damage other substances with which it is brought in 

 contact, and which is especially adapted to the particular purpose 

 for which it is used. 



An Antiseptic is a substance or agent that temporarily 

 inhibits or retards the growth and multiplication of micro- 

 organisms. 



A Deodorant is a substance used to remove or correct offensive 

 odours. 



Disinfectants may be Physical or Chemical. Among the former 

 are wind, sunlight, heat, and electricity. The latter may be in the 

 form of gases, solids, or liquids. 



Fresh air and wind are germicidal, though their action is slow. 

 Fresh air has an oxidising effect, which is enhanced if it is well 

 charged with ozone. Both fresh air and wind dry up moist dirt 

 that holds bacteria, and a drying wind dessicates micro-organisms. 

 Wind and fresh air entering an inhabited building dilute both the 

 excretory products of animals and the concentration of bacteria in 

 the air. 



Direct sunlight is a disinfectant in virtue of its violet and, more 

 especially, its ultra-violet rays. These rays are arrested by ordinary 

 window glass, so that sunlight transmitted through closed windows 

 has not the same power as if it passed through an open or unglazed 

 window. The rays are soon held in water, especially if the water 

 is turbid and holds much solid matter in suspension. Sunlight has 

 an oxidising and drying effect, so, while not necessarily a powerful 



