434 THE STOCK owner's ADVISER. 



canal by food and drink. All kinds of fungi swarm in the mouth. 

 Organisms are present in healthy bodies. They probably pass 

 continually through the pulmonary and intestinal mucous mem- 

 brane, but in small numbers. Such as ordinarily thus enter the 

 tissues are unable to develoj), so long as the body is healthy. All 

 organisms, perhaps, flourish best in tissues of Avhich the vitality 

 is impaired; some, probably, cannot develop unless this is the 

 case, and still others cannot multiply at all in living tissue. The 

 a-cute specific diseases, heretofore referred to, are now regarded 

 as forming a class of the much larger groups of infective diseases. 



An infective disease may be defined as a disease due to the 

 action of a poison or virus, which has the power of invading and 

 multiplying in living tissue. A contagious disease is communi- 

 cable only from individual to individual, the name implying 

 actual contact with the poison. Infectious diseases are communi- 

 cable without actual contact with the poison, the victim usually 

 being attacked from a distance. 



Bacteria are the causes of many diseases. Their classification 

 will not be given here. Parasites and diseases which they pro- 

 duce have been treated throughout this work. For fuller and 

 more particular treatment of the su'bject, the reader is referred 

 to special works on bacteriology. 



