RESPIRATION 187 



in the erect position, the absorption of a pleural exudate 

 may be favoured by allowing a patient to get up and 

 move about. A very large effusion, however, may stop 

 the action of the ' pump,' and in such a case removal of 

 part of it by aspiration may restart the mechanism, and 

 be followed by spontaneous absorption of the remainder. 



Compared with that of most other organs, the 

 lymphatic supply of the lungs is peculiarly abundant, 

 a circumstance which, whilst it undoubtedly predisposes 

 to rapid toxic absorption from the pulmonary surface, 

 also facilitates the speedy absorption of fluid or inflam- 

 matory exudates which have been poured out into the 

 alveoli. As the lung expands during inspiration the 

 stomata in the alveoli open up, and absorption is made 

 much easier. In accordance with this, one finds that 

 the clearing up of a pneumonic exudate often goes on 

 much more quickly if the patient is allowed to get up and 

 move about a little, for that ensures deeper breaths than 

 when he is lying in bed. It has been pointed out * that 

 there is much less variation in respiratory pressure 

 at the apices of the lungs than elsewhere. The blood 

 and lymph flow are thus not so well promoted in these 

 regions, with the result that they are apt to be less well 

 nourished than the rest of the lungs. The bearing of 

 this upon the special liability of the apices to become the 

 seat of tuberculosis has already been pointed out. 



The nerves of the lobule are derived from branches of 



the vagus, which supply motor twigs to the muscle of the 



bronchioles and sensory fibres to the alveoli. The 



broncho-constrictor fibres of the vagus are of great 



* Hofbauer, Zeit. f. Klin. Med., 1906, lix. 88. 



