introduction. 39 



Words Derived from Greek Roots. 



aster, a star. hudor, water. 



chronos, time. metron, a measure. 



ge, the earth. phone, a sound. 



gramma, a letter. polis, a city. 

 grapheim, to write. 



AETIOLOGY. 



What is meant by aetiology ? 



It is that division of general pathology that treats of the cause 

 of disease; or, it is the condition under which disease arises, or 

 the agents through which disease is produced. 



How may causes be divided? 



We may divide causes into predisposing and exciting; they 

 may also be divided into internal and external. 



What are predisposing causes? 



They are certain influences or conditions of the animal body 

 which disposes it to the action of disease by the application of some 

 exciting factor, and may be inherited or acquired. 



Anything that will place one or more tissues of the body in 

 such condition as to favor the growth, development, and multipli- 

 cation of micro-organisms is a predisposing cause. 



Define exciting causes. 



Exciting causes are those micro-organisms, ptomains, or 

 toxins which may excite disease by operating on an already pre- 

 disposed body. 



What is included under internal or intrinsic causes ? 



Internal or endopathic causes include heredity, age, previous 

 disease, breed or variety, temperament, idiosyncrasy or diathesis. 



The external or exopathic causes include what? 



External or extrinsic causes include atmospheric influences, 

 temperature (extreme heat or cold), faulty diet, work, defective 

 sanitary conditions, mechanical causes, micro-organisms, etc. 



What can be said in regard to the causation of com- 

 municable diseases of to-day as compared with the 

 past? 



The advancement of the science of bacteriology has placed the 

 aetiology of communicable diseases on a new basis. 



It is now a recognized fact that pathologists of to-day do not 



