CATARRHAL DISEASES. 



the outer coat of almost every internal organ. Hence the disease 

 may localize itself in many different parts of the body, and be 

 marked by many different symptoms. 



The Causes'. — We place as the first cause those influences, of 



Fig. 1275.— Lower Jaw of Nine-months Pig. 



whatever nature, which interrupt the perspiratory action of the skin. 

 Exposure* to showers, sudden changes of temperature, and insuf- 

 ficient protection from the night air, are among these influences. If 



Fig. 1276.— The Poland-China. 



the functions of the skin are interrupted, additional work is thrown 

 upon the lungs and kidneys. This fact is familiar to any one who 

 has ever suffered from a severe common cold. Hence those organs 

 with the mucous and serous membranes, are the first to be affected 

 by the disease. 



