42 PATHOLOGY. 



functions besides those already mentioned, the act of couglilng 

 and the varieties of cough demand our careful attention. 



A cough is a violent spasmodic action, and the sound is pro- 

 duced by a sudden and forcible expiration, preceded by a lirm 

 closure of the glottis ; and is for the most part an involuntary 

 effort to remove some source of irritation from the lungs, trachea, 

 or larynx. 



The varieties of cough which are met with in veterinary 

 practice are denominated moist, dry, short, hacking, violent, 

 spasmodic, the broken-winded cough, and the cough of the roarer. 



The moist cough attends cattarrh, bronchitis, and other diseases 

 where the secretion of the mucous follicles of the air passages is 

 increased. 



The dry cough indicates a non-secretory condition of the air 

 passages, and is usually present during the early stages of 

 catarrhal affections. In pleurisy the dry cough remains through- 

 out the disease ; it is also painful, short, and hacking, from the 

 pain which the forcible expiratory movement causes the animal 

 to feel. The dry cough has several modifications from that of 

 broken wind, where it is a miserable apology for a cough, to the 

 loud paroxysmal cough, caused by the irritation of teetliing, and 

 which may be properly named the dental cough, and the hollow, 

 sepulchral cough of the roarer. Cough does not always arise 

 from direct irritation of the air passages, lungs, or pleura, for we 

 often find an animal coughs when suffering from indigestion, 

 worms in the intestinal canal, diseases of the liver, &c. These 

 sympathetic coughs are always characterised by dryness. 



THE SYMPTOMS AFFORDED BY THE SECRETIONS. 



The secretions maybe either diminished, increased, or perverted. 

 In the early stages of inflammatory disease of a secretory organ, 

 it secretory function becomes diminished. Thus, in the first 

 stages of pleurisy the surfaces of the serous membrane are dry 

 and rub against each other, producing the " friction sound;" but 

 as the disease advances some of the natural fluid secretion of 

 the membrane, along with a quantity of inflammatory products 

 in a fluid state, is thrown out, and the surface, which was dry, 

 becomes unnaturally moist. The same changes occur when a 

 mucous membrane or a gland is inflamed. In the febrile state 



