INFECTIOUS DISEASES OF SWINE 



Germ Diseases. — In the past thirty years a great amount of 

 knowledge has been obtained relative to the cause of many diseases 

 which previous to that time had been believed to be due to con- 

 ditions producing changes in the ground or in the air. Such dis- 

 eases were often referred to as being due to a miasma. The renowned 

 Dr. Koch, of Berlin, Germany, was one of the founders of the germ 

 theory of disease, and we now know that a great number of dis- 

 eases which we formerly were unable to understand are produced by 

 some form of germ. In a great many instances the specific germ 

 which causes the condition has been isolated and proved to be the 

 cause of the mischief. For instance, in tuberculosis we now know 

 that the disease is due to a special form of germ which is known 

 as the bacillus of tuberculosis. The germs that cause sickness in 

 man or in animal are of such small size that they can be seen 

 only with the most powerful microscopes. 



When examined under the microscope some germs are seen 

 to be long and narrow in appearance. These are called bacilli. 

 According to this plan, the germ which causes typhoid fever in 

 man, being a long rod-shaped germ, is called the typhoid fever 

 bacillus. In like manner, the large rod-shaped germ that produces 

 anthrax in farm animals is known as the anthrax bacillus. An- 

 other type of germs are seen under the magnifying lenses as 

 round, dot-like bodies. These are known as cocci. For instance, 

 if the pus from a simple abscess be examined it will be found to 

 contain a large number of these rounded germs, which are known 

 as staphylococci. Sometimes these round germs are seen arranged 

 in long thread-like chains. They are then called streptococci. 

 Still another form of germs are seen which have a corkscrew-like, 

 spiral appearance. These are classed as spirilla. 



Definition. — Any disease which is caused by a germ is known as 

 a germ disease or, more commonly among the profession, as infec- 

 tious disease. By an infectious disease we mean, then, a disease 



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