RESPIRATORY APPARATUS 103 



4. In diseases of the heart which have a congestion of 

 the blood in the lungs as a consequence. 



II. If the respirations are labored ( alteredinqual- 

 i t y ) , though the frequency may be normal, aggravated dysp- 

 nea. The occurrence of respiratory noises 

 a 1-w ays indicates a difficulty in breathing. 

 Depending upon whether the expiration or inspiration is dif- 

 ficult, an expiratory or inspiratory dyspnea is distinguished. 



The inspiratory dyspnea. If the entrance of 

 air into the respiratory organs is made difficult, the animal 

 seeks to overcome the condition by taking forced inspirations. 

 N ot only is the diaphragm actively employed, 

 butothermuscleswhicharenormallynotused 

 during inspiration are called into play. 

 These muscles are: the serratus magnus, serratus anticus, 

 external intercostals, levatores, costarum, scalenus. The 

 following clinical symptoms character- 

 ize dyspnea: 



The nostrils are widely distended ; dogs fowls, cattle and 

 swine breathe with their mouths open. Dogs sometimes close 

 the jaws and breathe through the lateral commissures of the 

 mouth, sucking in the cheek at each inspiration. The head 

 and neck are extended horizontally, the larynx is retracted, the 

 ribs greatly elevated and rolled forward. The forelimbs are 

 spread far apart and the elbows turned out so that the serrati 

 and pectoral muscles can better come into play. 



If, in aggravated inspiratory dyspnea, the air enters the 

 lung very slowly, notwithstanding that the ribs are greatly 

 elevated, and the thorax is distended to a degree which does 

 not correspond to the quantity of air passing in, a suction 

 pressure will occur, which can be recognized by a sinking of 

 the lower anterior thoracic wall — particularly of its inter- 

 costal spaces. 



