CAUSES, SYMPTOMS, AND CLASSIFICATION OF DISEASE. 9 



lead ; and vegetable poisons, as the yew tree, hellebore, 

 and the rhododendron. 



8. Parasites— Animal and Vegetable. — Animal parasites 

 will be considered in detail in a later chapter. 



Vegetable parasites are most potent sources of disease. 

 When treating of Bacteria we shall see that these vegetable 

 fungi have been demonstrated in the blood and tissues of 

 animals suffering from many diseases. As an example, 

 anthrax or charbon will for the present suffice. 



In addition, parasitic fungi are frequently developed on 

 the external parts of the body, producing definite disorders, 

 but not invading the system at large. 



The so-called Tinese are examples of such diseases. They 

 are produced by the growth of parasitic fungi, such as the 

 Trichophyton tonsurans and Achorion Schonleinii. 



SEMEIOLOGY. 



By semeiology (ai^nuov, sign, and Xoyog, law) we mean the 

 science of the signs or symptoms manifested by the diseased 

 animal. 



Symptoms are local or general, according as they are 

 restricted to a special part or affect the system as a 

 whole. 



They are called primary when they arise directly as a 

 result of the disease ; sympathetic or secondary when 

 arising from those caused by the primary disease or from a 

 secondary disorder. 



They are called premonitory when they precede the full 

 development of the disease. And symptoms are still 

 further divided into diagnostic, prognostic, and therapeutic, 

 according as they are respectively applicable to the distinc- 

 tion, the determination of the result, and the suggestion of 

 the treatment, of the disease. 



