ATTENUATION OF BACTERIA 33 



lymph channels they are carried to the various mucous surfaces 

 of the body, intestinal and bronchial. The liver, according to 

 Adami, destroys at once bacteria absorbed from the intestines. 

 During typhoid fever, the typhoid bacilli are often found in 

 the urine, the organisms escaping from the blood or from the 

 lymphoid foci in the kidney. Pathogenic bacteria are discharged 

 from the body in feces, pus, sputum, and in scales in the des- 

 quamating skin diseases. 



To successfully inoculate a guinea pig with tuberculosis, the 

 tubercle bacilli should be injected beneath the skin. 



It has been said that successful invasion demands a sufficient 

 number of organism; it is equally true that the number admitted 

 will determine the character of disease to arise, as is indicated 

 by the following observation of Cheyne. 



In experimenting with the staphylococcus aureus, it was found 

 that 250,000,000 were required to cause an abscess; and 1,000,000,- 

 ooo were needed to cause death. The internal powers of defense 

 were able to cope with or limit the action of a few million to a 

 certain locality, but could not withstand the injection of over- 

 whelming numbers, which caused the animal's death. 



There are three attributes which make successful the invasion 

 of pathogenic germs into the body: virulence, toxicity and 

 pathogenicity. These factors shade into each other sometimes 

 very confu singly and are of course capable of varying proportions 

 in the same organism. In order to combat successfully the pri- 

 mary defenses of the body, a virus requires virulence, the degree 

 and permanency with this is accomplished being due to the amount 

 of poison the invader can elaborate to keep the safety devices 

 of the economy from conquering. The physical damage done 

 is attributable to the pathogenicity of the germ. It is like a 

 fight where the man has strength, and staying powers and does 

 physical damage to his adversary. 



Ehrlich's explanation of virulence assumes that bacteria have 

 binding posts or receptors and the more of these a germ has, the 



