312 CLINICAL APPLIED ANATOMY. 



mitral valve. When bronchitis is accompanied by emphysema 

 a considerable area of pulmonary capillaries disappears. The 

 capillaries are derived from the pulmonary arteries which supply 

 the alveoli, hence the pressure is raised in these vessels, so 

 hypertrophy and dilatation of the right ventricle result. 



The lungs of infants and young children differ markedly from 

 those of adults. In early life the interstitial tissue forms a con- 

 siderable part of the lung and is highly vascular ; the alveoli are 

 comparatively small and thick walled, and the extent of the 

 bronchial tubes is proportionately greater than that of the air 

 spaces. Consequently the breath sounds are not damped by the 

 pulmonary parenchyma to such an extent as in the adult, but 

 are harsh or even bronchial, and may give rise to a suspicion of 

 broncho-pneumonia when none is present. In children, as a 

 consequence of the anatomical conditions, vascular distension 

 and interstitial infiltration form a marked feature in broncho- 

 pneumonia, the small alveoli are much more easily plugged, and 

 pulmonary collapse is readily induced by trivial inflammations. 

 The yielding character of the chest wall in infancy, and the 

 feeble respiratory movements, also contribute to the production 

 of collapse of the lung. 



LOBAR PNEUMONIA. 



A knowledge of the relations of the fissures of the lungs to the 

 back, sides and front of the chest is essential for the determina- 

 tion of the site and the extent of the lesion in lobar pneumonia. 



The great fissure, which separates the upper lobes of the lungs 

 from the lower parts, extends from the second dorsal spinous 

 process across the infraspinous fossa of the scapula, traverses the 

 axilla near the fourth rib, and terminates in front close to the 

 sixth costal cartilage near the parasternal line. The other parts 

 of this great fissure lie on the inner surface and base of the lung, 

 and, consequently, cannot be indicated on the surface of the 

 chest. If the elbow on the side examined be well raised above 

 the level of the shoulder, and the palm of the hand carried over 



