NONCONTAGIOUS DISEASES OF RESPIKATOEY ORGANS. 89 



The secretions. — The secretions may be diminished, increased, or 

 perverted. In the early stage of an inflammation of a secretory or- 

 gan its secretion is diminished. In the early stage of pleurisy the 

 serous membrane is dry, and as the disease advances the membrane 

 becomes unnaturally moist. The products of secretion are sometimes 

 greatly changed in character from the secretion in health, becoming 

 excessively irritant and yielding evidence of chemical and other 

 alterations in the character of the secretion. 



Cough. — Cough depends upon a reflex nervous action and may be 

 primary when the irritation exists in the lungs or air passages, or 

 secondary when caused by irritation of the stomach, intestines, or 

 other parts having nervous communications with the respiratory ap- 

 paratus. A cough is said to be dry. moist, harsh, hollow, difficult, 

 paroxysmal, suppressed, sympathetic, etc., according to its character. 

 It is a very important symptom, often being diagnostic in diseases of 

 the respiratory organs, but this is a subject, however, which can be 

 more satisfactorily treated in connection with the special diseases of 

 the organs in question. 



Resjnration. — In making an examination of an animal observe the 

 depth, frequency, quickness, facility, and the nature of the respira- 

 tory movements. They may be quick or slow, frequent or infre- 

 quent, deep or imperfect, labored, unequal, irregular, etc., each of 

 which indications has its significance to the experienced veterinarian. 



Sleep, rumination, pregnancy in cows, etc., modify the respiratory 

 movements e^en in health. Respiration consists of two acts — inspira- 

 tion and expiration. The function of respiration is to take in oxygen 

 from the atmospheric air, which is essential for the maintenance of 

 life, and to exhale the deleterious gas known as " carbon dioxid." 



The frequency of the respiratory movements is determined by 

 observing the motions of the nostrils or of the flanks. The normal 

 rate of respiration for a healthy animal of the bovine species is 

 from 15 to 18 times a minute. The extent of the respiratory sys- 

 tem renders it liable to become aifected by contiguity to many parts 

 and its nervous connections are very important. 



Rapid, irregular, or difficult breathing is laiown as dyspnea, and 

 in all such cases the animal has difficulty in obtaining ?.s much oxygen 

 as it requires. Among the conditions that give rise to dyspnea may 

 be mentioned restricted area of active lung tissue, owing to the fill- 

 ing of portions of the lungs with inflammatory exudate, as in pneu- 

 monia ; painful movements of the chest, as in rheumatism or pleurisy ; 

 fluid in the chest cavity, as in hydrothorax; adhesions between the 

 lungs and chest walls ; compression of the lungs or loss of elasticity ; 

 excess of carbon dioxid in the blood: weakness of the respiratory 

 passages: tumors of the nose and paralysis of the throat: swellings 



