210 PRINCIPLES OF VETERINARY SCIENCE 



to bring the viscera to view. After careful inspection of the 

 exposed organs for pathologic changes, the carcass maybe inclin d 

 to one side, and the stomach, intestines, spleen, bladder, and 

 other soft organs removed for a more detailed examination. 

 Care should be used to avoid puncturing the hollow organs, for 

 their contents will escape and may seriously interfere with 

 further work. 



The incision, made when the abdomen was opened, should be 

 carried forward to the throat. At this time it will be best to 

 examine the nasal cavity, pharynx, esophagus, and trachea. 

 In order to get at the organs in the thoracic cavity it will be 

 necessary to divide the sternum or breast bone in its length. 

 Especial note should be made of fluid found in this cavity. An 

 excessive quantity indicates pleurisy. Adhesions of the lungs 

 to the inner sides of the ribs are found as a result of inflammatory 

 changes in the lungs. Healthy lung tissue is soft and spongy, 

 If pneumonia is present, dark-red, firm areas will be found. 



(3) A Biologic Examination. — The recognition of the patho- 

 genic organism, its products, and the effects of these upon the 

 animal tissues are included in the biologic examination. It is 

 often necessary, in order to establish the actual cause of 

 infectious and parasitic diseases, to examine the secretions, body 

 fluids, and tissues with the aid of a microscope. Such an ex- 

 amination is useful while the animal is sick as an aid to rational 

 treatment, and very valuable after death in showing what 

 measures should be followed to protect other animals from a 

 similar infection. In doubtful cases an experimental animal is 

 inoculated with blood or pus from the suspicious subject. 

 Within the last few years several different laboratory tests of 

 the blood-serum and milk have been used to point out diseased 

 animals. Those of practical value are the complement-fixation, 

 agglutination, and precipitation tests. 



When the general and special examinations have been made, 

 a conclusion as to what disease actually exists is arrived at by the 

 processes of comparison and elimination. The changes that 

 occur in the various possible diseases are reviewed and con- 

 trasted with those presented by the subject. This reveals 

 similarities to the examiner from which, in most cases, he should 

 be able to make a definite diagnosis. 



After the diagnosis has been established, the prognosis, which 



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