30 INFECTION 



In rheumatic fever, measles, whooping-cough, poliomyelitis, 

 mumps, yellow fever, typhus fever, chicken-pox, rabies, and dengue, 

 the specific cause has, thus far, eluded discovery. In the case of 

 yellow fever (Reed and Carrol) and hog cholera, it has been found 

 that the cause of these diseases resides in the blood, and if the 

 serum of the latter is carefully filtered through a Berkefeld filter, 

 it is still capable of producing the disease in susceptible animals. 

 Careful microscopic search fails to show any bodies in the serum 

 that might be considered the agents of infection, and it is thought 

 that these organisms are submicroscopic. 



If the invading organism is a pure saprophyte the various forces 

 for internal defence immediately act upon and destroy it. If it is 

 pathogenic for other animals, their defensive agencies have no effect 

 upon it in their tissues, but in the human body the bacteriolysins 

 dissolve it, or the phagocytes devour it and carry it away. The 

 liver, according to Adami, destroys at once bacteria absorbed from 

 the intestines. 



Bacteria are disposed of in divers ways, by means of the lymph 

 channels they are carried to the various mucous surfaces of the 

 body, intestinal and bronchial. During typhoid fever, the typhoid 

 bacilli are often found in the urine. The kidneys at least allow 

 the escape of some organisms from the blood. Pathogenic bacteria 

 are discharged from the body in feces, pus, sputum, and in scales 

 in the desquamating skin diseases. 



To successfully inoculate a guinea pig with tuberculosis, the 

 tubercle bacilli should be injected beneath the skin. 



In working with infections produced by the B. proteus vulgaris, 

 it was found by Watson Cheyne that 6,000,000 bacilli injected 

 under the skin, did not produce any lesion; 8,000,000 formed an 

 abscess; 56,000,000 gave rise to a phlegmon; and 225,000,000 were 

 necessary to cause death in two hours. 



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 



