RESPIRATORY APPARATUS. 99 



When the abdominal muscles are more active in produc- 

 ing the respiratory movement than the thoracic muscles the 

 type of breathing becomes abdominal. The abdominal type 

 prevails when painful conditions of the chest wall are present 

 «md where expiration is difficult, as in pulmonary emphysema 

 (heaves). 



4. There is sometimes observed in animals a condition 

 corresponding to hiccoughs {singultus) in man. It is character- 

 ized by a rhythmic, spasmodic contraction of the diaphragm, 

 (abdominal pulsation) with which a jerky movement of the 

 thorax in the hypochondriac region occurs. Occasionally it 

 is accompanied by a dull sound. Its rhythm is synchronous 

 with neither the heart's beat nor the respirations. The latter, 

 however, are temporarily arrested by the spasms. Singultus 

 is usually temporary and probably due to a diaphragmatic 

 neurosis. 



C. Respiratory Sounds. 



The respirations of healthy animals are performed noise- 

 lessly. Only occasionally do they voluntarily emit audible 

 sounds during the act of breathing. 



Physiological Sounds. When excited suddenly by 

 perceiving peculiar looking objects, strange persons, unaccus- 

 tomed odors, etc., horses and cattle snort by violently and 

 noisily forcing air through the dilated nostrils. Horses of 

 lively temperament usually snort when led at the end of the 

 halter. Horses blow their noses by causing a forced expira- 

 tion which is accompanied by a vacillating noise. As in man, 

 dust or mucus is thus removed from the nasal organs. Fat, 

 rough coated dogs pant when the weather is warm even when 

 they are at rest. While performing hard work or during 

 forced exercise the breathing is rapid and deep ; the air pass- 

 ing in and out of the dilated nostrils at each in- and expiration 

 produces a perceptible puffing sound. Spirited horses while 

 being ridden at a gallop, emit a blowing expiratory sound 

 every time the forefeet come in contact with the ground. 



