236 GENERAL BIOLOGY 



The Inheritance of Disease. Disease, to primi- 

 tive man, must have seemed a very mysterious 

 thing, a fiend or evil god to be placated or exorcised. 

 Popular therapeutics in some parts of the world is 

 still based upon such an hypothesis. Even in civi- 

 lized society, the belief is still widely prevalent that 

 disease is a sort of entity, to be gotten rid of, not 

 perhaps by the bells and the tom-toms of the medi- 

 cine man, but by the agency of drugs. Our grand- 

 mothers thought that boils were " better out than 

 in," and took noxious doses for the purpose of 

 " cleansing the blood " of them. We now know 

 that disease is a process, not an entity. When my 

 watch loses time because it needs cleaning, we might 

 say that it runs "abnormally." The dust in the 

 works is the cause of the condition, but it itself is 

 not the abnormality ; the abnormality is the slowing 

 down of the movement. In the same way, ab- 

 normalities in the " running " of the human machine 

 are due, in the majority of cases, to the presence 

 therein of foreign bodies which bring about the 

 altered conditions. Usually these microbes ;u< 

 bacteria, though sometimes they are minute pro- 

 tozoa. They are merely parasites that, in si riving 

 to get a living for themselves on the tissues of their 

 host, produce poisons as an incidental result of their 

 activity. These poisons produce the alterations 

 in metabolism we call disease. If we can get rid 

 of the active agents, the disease is cured, provided 

 the damage has not gone too far. This may be 

 done either directly (sterilization) or indirectly by 



