102 CLINICAL DIAGNOSTICS. 



pressure of the distended abdominal organs upon the dia- 

 phragm, shortening the expiratory moment, which the animals 

 seek to retard by partially closing the' glottis. 



d. Labored Breathing, Dyspnea. 



The collective term dyspnea is applied 

 to essential deviations from the normal in 

 the frequency and kind of respiratory move- 

 ments, and the occurrence of accompany- 

 ing pathological sounds. 



Physiologically a dyspnea occurs whenever the blood 

 flowing through the respiratory center contains an abnormal 

 amount of CO;.. Accordingly, anything which increases the 

 quantity of C0 2 in the tissues, or interferes with the exchange 

 of gases in the lungs, can cause a dyspnea. 



Clinically the presence of dyspnea is recognized : 



I. If the respirations are accelerated (altered in 

 number ), and the increased frequency is not attended with 

 change in the manner of breathing the dyspnea is simple. 



In the horse, for instance, the number of respirations can 

 exceed 80-100 per minute and be superficial, only the nostrils 

 becoming dilated. 



If the dyspnea is severe, however, the intensity of the 

 respirations is increased. 



Simple dyspnea appears : 



1. In fever; the degree of respiratory frequency de- 

 pends upon the severity and nature of the disease. 



2. In all conditions which make the respiratory act 

 painful : diseases of the pleura, diaphragm, thoracic wall, 

 peritoneum. 



3. Where the breathing surface of the lung is decreased 

 or where the organ is prevented from properly expanding: 

 pneumonia, pulmonary tuberculosis, abdominal tympanitis, 

 ascites. 



