RESPIRATION IN MAN 185 



the varying degree of extensibility of the structures of the lung. 

 In all mammalian lungs the veins and arteries occupy a definite 

 and constant relationship to the bronchial ramifications a relation- 

 ship which must have a functional significance. Amongst the 

 various means the writer employed to estimate the extensibility of 

 the several parts and structures of the lung was that of marking the 

 surface of the partly inflated organ with points placed at regular 

 intervals, and then measuring the distances between these points 

 when the lung was more fully inflated. The parts of the lung 

 which were found to expand most were the central areas of the 

 costal and of the diaphragmatic surfaces. The method was 

 abandoned because it was found that the expansion obtained by 

 inflating the lung did not correspond to the expansion of the lung 

 by means which imitated the normal action of the thoracic walls. 

 Hutchinson discovered long ago that the form assumed by the 

 thorax when the lungs are inflated after death, differs altogether 

 from the inspiratory position of the thorax. His observation, 

 however, has been forgotten, and models of lungs so inflated are at 

 present the only ones on the market. Several anatomical papers 

 have been published recently giving the inspiratory position of the 

 apices of the lungs, that position being determined by artificial 

 inflation of the lung. In the dead body the lung, when inflated, 

 expands in the direction of least resistance. 



ON THE FUNCTION AND NATURE OF THE INFUNDIBULA 



Closely related to the extensibility of the various elements of the 

 lung is the question of the function and nature of the infundibula. 

 In the most valuable work recently published by Oppel the use of 

 the term infundibulum is condemned. He prefers to follow Miller 

 in distinguishing the following terminal air spaces in the lung : 



(1) The terminal bronchiole, with its sphincter-like arrange- 

 ment of musculature ; (2) the vestibule ; (3) the atrium ; (4) the 

 air sacs ; (5) the alveoli implanted on the walls of the air sacs. 



Such an elaborate nomenclature obscures the functional nature 

 of the final pulmonary elements, for while the terminal bronchus 

 is one functional element, and the alveoli another, the vestibule, 

 the atrium, and air sacs combined form but one element, namely, 

 the essential distensible air spaces of the lung (bellows part), and 

 it is well to retain the term infundibulum to designate the com- 



