49 8 IOWA DEPARTMENT OF AGRICULTURE 



for the reason that they contain spores. A spore may be likened to the 

 seed of a plant, for It bears about the same relation to the bacillus that 

 a grain of wheat does to the plant proper. As the plant may be destroyed 

 and the iseed remain latent for an indefinite time, so destruction of the 

 bacillus may be easUy accomplished while the spores remain unharmed 

 and retain life for weeks or months. 



An example of this class of organisms is seen in the agent "which 

 causes anthrax {BaciVus anthracis). Ordinarily methods for the de- 

 struction of the bacillus will not destroy the spore as well, and thus 

 anthrax becomes a most difficult disease to eradicate. Upon farms where 

 animals have died from anthrax and the carcasses have been buried in- 

 stead of destroyed, repeated outbreaks of the disease may occur from 

 time to time, possibly extending over a period of several years. This con- 

 dition is due to the existence of the very resistant spores, which under 

 favorable circumstances are carried to the surface of the earth and be- 

 come infecting organisms — much as the seed of a noxiovs weed, after re- 

 maining in the soil during the winter, finds the conditions favorable in 

 the spring and develops into a plant — except that these minute forms of 

 life multiply with the most wonderful rapidity. 



Thus it is that cur increased knowledge regarding microorganisms or 

 bacter'a as the cause of many animal diseases has emphasized the import- 

 ance of disinfection. 



THE NATUEE OF DISINFECTION, 



The work of disinfection is based upon our recognition of the presence 

 of disease germs, and disinfection means the act of destroying the cause 

 of the infection. In other words, disinfection is a removal of the cause, 

 and it will be clear to any practical man that in dealing with disease 

 any effort which stops short of a complete removal of the cause is m.ost 

 unwise and unprofitable. To those unaccustomed to the work, disinfection 

 may seem a most complicated process. Any approved method, however, 

 is comparatively simple when carried out carefully, although like many 

 another procedure it is one in which attention to deta'ls counts for much. 

 It is important to bear in mind that the causative agents of many dis- 

 eases are extremely small and may remain for an indefinite time in dust, 

 cracks, and crevices of buildings, so that efforts aiming at the eradica- 

 tion of disease from contaminated premises must be thorough in order 

 to be effective. 



DISINFECTANTS. 



In the work of disinfection nature has provided man with a most valu- 

 able ally — sunlight. It is well known that the direct rays of the sun 

 are destrrstive to many forrrs of bacteria, in some cases destroying them 

 and in others lessening their influence. Thus the importance of well- 

 lighted stables is evident. The dark and sunless building will be a 

 favorable breeding place for bacteria, and the structure which admits 

 the greatest amount of sun'Ight will be the least favorable for their 

 development. Again, heat wnll destroy the bacteria of disease. But this 

 Is not meant the ordinary heat of the sun, but heat as developed in 

 boiling water or in flame. It is upon this principle that the surgeon 



