872 OF RESPIRATION. 



former are paralyzed, the respiratory movement is confined to the diaphragm : 

 this is insufficient, and with the coincident paralysis of the vaso-motor 

 nerves leads to the effusion of serum into the lungs, and slow asphyxia, 

 which usually proves fatal in a few days. Even where the muscles and 

 nerves are all capable of action, the full performance of the inspiratory 

 movements is prevented by the solidification or engorgement of any part of 

 the lung which interferes with its free distension ; or by adhesions between 

 the pleural surfaces, which offer a still more direct impediment. When 

 these adhesions are of long standing, they are commonly stretched into 

 bands, by the continual tension to which they are subjected. If the imped- 

 ing cause affect both sides, the movements of both will be alike interfered 

 with ; but if one side only be affected, its movements will be diminished, 

 whilst those of the other remain natural ; and the physician hence fre- 

 quently derives an indication of great value, in regard to the degree in 

 which the lung has become incapable of performing its functions. It is to 

 be remembered, however, that the action both of the diaphragm and of the 

 elevators of the ribs may be prevented, by pain either in the muscles them- 

 selves or in the parts which they move; thus the descent of the diaphragm 

 is checked by inflammation of the abdominal viscera or of the peritoneum ; 

 and the play of the intercostals by rheumatism, pleuritis, pericarditis, or 

 other painful disorders of the parts forming the parietes of the thorax. In 

 man the acts of respiration are properly effected through the nostrils, which 

 are lined by a highly vascular membrane, kept constantly moist by numer- 

 ous glands, and by the lachrymal secretion, whilst its surface is greatly ex- 

 tended by the sinuosities of the turbiual bones. The inspired air is thus 

 rendered moist and warm before reaching the sensitive larynx and lungs, 

 and the coughs and colds so prevalent in this country in the winter and 

 spring months might often be avoided if care were taken, especially on sud- 

 den exposure to cold air, to breathe through the nostrils instead of the mouth. 

 The passage of air into and from the lungs is accompanied by a peculiar 

 soft blowing sound, termed the respiratory murmur or bruit. The act of in- 

 spiration being more rapid and energetic than that of expiration, is attended 

 by a louder sound, which is most distinctly audible in young children and 

 in thin persons. It probably arises either, as Dr. Salter 1 suggests, from the 

 current of air striking against the angles of division of the bronchia, or, as 

 indicated by Dr. Waters, 2 from a slight constriction that exists at the mouth 

 of each air-sac. Other causes that have been assigned to it are the separa- 

 tion of the moist septa of the alveoli, the general friction of the air against 

 the walls of the bronchial tube, and the reverberation of the glottidean 

 bruit (Sabaiier ; Cornil, 1873). The expiratory murmur is exclusively due 

 to the friction of the air against the glottis (Chauveau). 3 



291. The relative amount of muscular force which is required for the 

 two respiratory movements respectively is affected in a very remarkable 

 manner by the elasticity of the walls of the thoracic cavity and of the lungs 

 themselves; for this (like the elasticity of the lungs) supplies a force which 

 greatly aids the expiratory movement, whilst it offers a corresponding oppo- 

 sition to the inspiratory. Here, also, the degree of force exerted increases 

 very rapidly with the degree of distension. Thus in a body experimented 

 on by Dr. Hutchinson, 4 the following were the relations between the amount 

 of air forced in, the resisting elasticity, as shown by the height of mercury 

 supported, the actual pressure upon each square inch of surface which this 



Pamphlet on Cause of Respiratory Murmur, 1864. 



i 



2 Mecl.'-Chir. Kev., 1805, p. 217. 

 See Budge, Compendium de la 



3 See Budge, Compendium de la Physiologic, 1874, p. 69. 



4 Op. eit., p. 1056. 



