NONCONTAGIOUS DISEASES OF RESPIRATION ORGANS. 87 



is seen in serious diseases of the respiratory tract, such as pneumonia 

 and in heart failure. 



The secretions. — The secretions maybe either diminished, increased, 

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

 organ 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 some- 

 times 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 sec- 

 ondary when due to irritation of the stomach, intestines, or other 

 parts having nervous communications with the respiratory apparatus. 

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

 suppressed, sympathetic, etc., according to its character. Cough is 

 a very important symptom, often being diagnostic in diseases of the 

 respiratory organs; but this is a subject which can be more satisfac- 

 torily treated in connection with the special diseases of the organs in 

 question. 



Respiration. — 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 infrequent, 

 deep or imperfect, labored, unequal, irregular, etc. , each of which has 

 its significance to the educated and experienced veterinarian. 



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

 movements even 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 

 fifteen to eighteen times per minute. The extent of the respiratory 

 system renders it liable to become affected by contiguity to many 

 parts, and its nervous connections are very important. 



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

 the animal in all such cases has difficulty in obtaining the amount of 

 oxygen that it requires. Among the conditions that give rise to dysp- 

 nea may be mentioned restricted area of active lung tissue, due to 

 filling 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 dioxide in the blood; weakness of the respiratory 

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



