GENERAL STRUCTURE OF THE RESPIRATORY ORGANS. 509 



Fig. 146*. 





Bronchial termination in 

 the lung of the dog. a. 

 Tube (lobular passage) 

 branching towards the in- 

 fundibula. 6. One of the 

 infundibula. c. Septa pro- 

 jecting inwards on the in- 

 fundibular wall and form- 

 ing the alveoli, or cells. 

 From JRossignol. 



Thin slice from the pleural surface of a cat's lung, considerably magnified. At the thin edge, bed, alveoli 

 are seen. In the centre (as a) where the slice is thicker, alveoli are seen on the walls of infundibuto. From 

 Rossignol. 



structure. He insists particularly on the ultimate bron- 146f. 



chial ramifications being in shape like an inverted funnel, 



and he terms them the infundibula. The cells, forming 



a honeycomb on their interior, he calls the alveoli (Figs. 



146* and 146f). Emphysema, according to this author, 



seems to consist in a distension of the passages and cells, 



and a breaking down and obliteration of the septa, first 



between the cells of the same passage and then between 



neighboring passages, and even between contiguous 



lobules. 



The diameter of the lobular passages is from y^ tn * 

 2^o-th of an inch ; and that of the cells from ^--^th to g^th 

 of an inch according to our measurements. In a prepara- 

 tion of the lung of the calf, by Professor Retzius, they 

 measure g-^th ; and Dr. W. Addison makes them from 

 s^g-th to T *^th of an inch. ED. 1 ] 



542. The fibrous coat of the bronchial tubes possesses a considerable amount 

 of muscular contractility, which (according to the experiments of Dr. 0. J. B. 

 Williams) 3 may be excited by electrical, chemical, or mechanical stimuli, ap- 

 plied to themselves, but this is not so readily excitable through their nerves, 

 although the experiments of Volkmann 3 and Longet 4 have clearly shown the 

 possibility of thus calling it into action. This contractility resembles that of 

 the intestines or arteries, more than that of the voluntary muscles or heart; the 

 contraction and relaxation being more gradual than that of the latter, though 

 less tardy than that of the former. It is chiefly manifested in the smaller bron- 

 chial tubes, those of less than a line in diameter having been seen to contract 

 gradually under the stimulus of galvanism, until their cavity was nearly obli- 

 terated ; on the other hand, in the trachea and the larger bronchi, the cartilagi- 

 nous rings prevent any decided diminution in the caliber of the tubes, and the 

 muscular structure is much less distinct. It is remarked by Dr. Williams, that 

 the contractility of the bronchial muscles is soon exhausted by the action of a 



1 "Physiological Anatomy," by Todd and Bowman, Am. Ed. 



2 "Report of the British Association for 1840," p. 411. 



3 "Wagner's Handworterbuch," art. "Nervenphysiologie," $ 586. 



4 " Anat. et Physiol. du Systeme Nerveux," torn. ii. p. 289. 



