Anatomical Changes. 95 



of development. On close inspection one may reco^-nize a minor 

 change in the respiratory movements; the expiration is some- 

 what prolonged and ocenrs with the auxiliary action of the 

 abdominal muscles. In less well nourished animals one sees 

 during inspiration a slight sinking in of the intercostal spaces 

 and of the wall of the thorax in the cardiac region. The fre- 

 quency of respiration is at first not changed. The animals 

 are, however, more easily tired during w^ork, and they breathe 

 then more rapidly; they show in short the symptoms of being 

 short of wind even at this early stage. 



In a more advanced stage the dyspnea, however, becomes 

 distinct. The ribs are now elevated strongly and moved for-' 

 ward, and there is strong passive sinking in of the intercostal 

 spaces of the lower portions of the thoracic wall, also of the 

 anterior aperture of the chest and of the flanks. Expiration 

 occurs under very strong auxiliary action of the abdominal 

 muscles and the formation of a depression along the costal 

 arches. The expiration is often double and is accompanied by 

 an upward movement of the lumbar portion of the spinal column 

 and by a shaking of the whole rump. The inspiration often 

 also occurs in two stages (see Fig. 10). The respiration is 

 usually somewhat accelerated. 



A lasting dilatation of the thorax progresses in like degree 

 with the gradual dilatation of the lungs. The more prominentlv 

 curved ril)s produce a barrel-shaped thorax, a picture which 

 betrays the character of the disease on first sight. 



The percussion sound over the lungs is deeper and markedly 

 loud. The increase in intensity is particularly marked over 

 the inferior margins of the lungs, wdiere a higher but duller 

 sound is heard under normal conditions. The area of cardiac 

 dullness becomes smaller or may disappear entirely. In severe 

 cases one can also show by weak percussion that the posterior 

 boundary of the lungs has been displaced backward and down- 

 ward. (In healthy horses which are not overly fat one finds 

 the posterior boundary of the lungs in the iliac line where 

 it is crossed by the seventeenth rib, in the ischial line by the 

 fifteenth rib; in the shoulder line by the eleventh rib; and 

 it passes into the lower horizontal boundary in the seventh 

 intercostal space ; in emphysema of a high degree, however, 

 the lungs reach to the eighteenth ril) in the iliac line, to the 

 seventeenth rib in the ischial line, and to the twelfth or four- 

 teenth rib in the shoulder line. [See Fig. 9].) 



On auscultation one hears weakened vesicular breathing, 

 often mixed with dry or moist rfdes as an indication of an 

 existing bronchial catarrh, which then also leads to an intensi- 

 fication of the vesicular breathing sounds over some portions 

 of the thorax. 



Cough is due to a more marked bronchial catarrh and 

 usually occurs in a somewhat more advanced stage of the 

 disease. It is weak in more pronounced cases of emphysema 



