THE RBSPIRATOEY SYSTEM. 403 



Bawling, neighing, braying, etc., are made up of long ex- 

 piratory acts, preceded by one or more inspirations. The vocal 

 cords are also rendered tense. 



SPECIAI. CONSIDERATIONS. 



Pathological and Clinieal. — The number of diseases that lessen 

 the amount of available pulmonary tissue, or hamper the move- 

 ments of the chest, are many, and only the briefest reference 

 can be made to a few of them. 



Inflammation of the lungs may render a greater or less por- 

 tion of one or both lungs solid ; inflammation of the pleura 

 (pleuritis, pleurisy) by the dryness, pain, etc., may restrict the 

 thoracic movements; phthisis may solidify or excavate the 

 lungs, or by pleuritic inflammation glue the costal and pulmo- 

 nary pleural surfaces together ; bronchitis may clog the tubes 

 and other air-passages with altered secretions ; emphysema (dis- 

 tention of air-cells) may destroy elasticity of parts of the lung; 

 pneuma-thorax from rupture of the lung-tissue and consequent 

 accumulation of gases in the pleural cavity, or pleurisy with 

 effusion render one lung all but useless from pressure. In all 

 such cases Nature attempts to make up what is lost in amplitude 

 by increase in rapidity of the respiratory movements. It is 

 interesting to note too how the other lung, in diseased condi- 

 tions, if it remain unaffected, enlarges to compensate for the 

 loss on the opposite side. When the muscles are weak, espe- 

 cially if there be hindrance to the entrance of air whUe the 

 thoracic movements are marked, there may be bulging inward 

 of the intercostal spaces. 



Normally, this would also occur, as the intra-thoracic press- 

 ure is less than the atmospheric, were it not for the fact that the 

 intercostal muscles when contracting have a certain resisting 

 power. 



The imperfect respiration of animals when dying, permitting 

 the accumulation of carbonic anhydride with its soporific 

 effects, smooths the way leading to the end; so that there may 

 be to the uninitiated the appearance of a suffering which does 

 not exist, consciousness itself being either wholly or partially 

 absent. The dyspnoea of anaemic animals, whether from sud- 

 den loss of blood or from imperfect renewal of the haemo- 

 globin, shows that this substance has a respiratory function; 

 while iu forms of cardiac disease with regurgitation, etc., the 



