20 



the terminal bronchial twig. The lobulette thus formed is sur- 

 rounded by its sheath, and no communication exists between it and 

 adjoining ones. 



That the appearances I have described in the artificially inflated 

 foetal lung are not the result of any abnormal distension, I have been 

 able to prove by observing the same appearances in the lung of a 

 child in which only partial respiration had taken place. 



Do the air-sacs communicate with each other by any orifices ex- 

 cept that by which they communicate with the bronchial tube ? 



Different opinions have been expressed on this point. Adriani 

 states that he has observed such orifices, and specially mentions 

 that they are most clearly to be seen in the stag. Dr. Thomas Wil- 

 liams considers that the " intercellular passages " intercommunicate, 

 and are perforated by secondary passages at every point. Rossignol, 

 Schultz, Mandl, and Milne-Edwards, deny the existence of such 

 communications. From observations, made with much care and 

 frequently repeated, I have satisfied myself that the opinion expressed 

 by the latter authors is correct. I have never found, either in the 

 lung of man or in that of the dog, cat, pig, sheep, or any other 

 mammal I have examined, any lateral orifices of communication 

 between the sacs of a lobulette. 



Alveoli of the Bronchial Tubes. The termination of the bronchial 

 tubes has a special character, first pointed out by Rossignol. He 

 says, " In the bronchial divisions of the two last, and sometimes three 

 last orders, it is plainly seen, when they are opened longitudinally, 

 that their surface is covered over, or, as it were, honeycombed with 

 a number of small, regular, shallow cavities, placed side by side, and 

 separated by thin perfect walls of the same height, which project 

 into the interior of the bronchial tube." The existence of these 

 bronchial alveoli has been noticed by subsequent observers ; they 

 may be easily seen in a lung injected and inflated, and sometimes 

 even in one which has been simply soaked in spirit for a few days ; 

 they resemble the alveoli of the air-sacs ; they are best seen in the 

 lungs of some of the lower animals, as the cat, in which they are 

 found in the ultimate bronchial tubes and their dilated extremities. 

 In man I have never seen them, except at the extremity of the 

 tubes ; and in many lungs I have found no appearance of them at 

 all they appear to become obliterated with advancing age. In the 



