GLANDS. 89 



J 



The primary lobules, thus described, grouped 

 together without any intermediate substance, consti- 

 tute secondary lobules. These latter have the shape 

 of pyramids, whose bases are directed towards the 



a piece of lung is well injected, the walls of the air-sacs become almost 

 entirely opaque ; their outline may be distinctly seen when they are 

 divided ; and, the vessels in their walls being filled with the dried gelatine 

 and coloring matter, dissections under the microscope can be carried on 

 with great facility, without which I believe it is impossible to form a 

 definite notion of the anatomy of these parts." With respect to injection 

 of the air-tubes, he remarks that, " when gelatine is used as a vehicle for 

 injecting the blood-vessels with some opaque matter, it usually happens 

 that the coloring matter is left in the vessels, and a portion of the trans- 

 parent gelatine exudes into the air-tubes ; and this has appeared to me 

 as good a way as any, of effecting an injection of this kind. Where such 

 a preparation is dried, and then soaked in spirit and water, it swells, and 

 assumes much the shape it has in its normal condition, and much infor- 

 mation may be derived from an examination of it. When a piece of 

 lung, in which the blood-vessels are injected, has injected into its air- 

 tubes a mixture of turpentine and wax, and is left to dry, and then a 

 slice of it moistened with Canada balsam, as suggested in Adriani's thesis 

 (Arius Adriani, Dissertatio anatomica inauguralis de subtiliori Pulmo- 

 num structurd, 1847, p. 41), the substance filling the air-tubes becomes 

 transparent, and the outline of the air-sacs and ultimate bronchial tubes 

 is well seen, and a very correct notion of their shape can be formed." 

 . . . . " If we follow out a bronchial tube on a lung thus injected, 

 inflated, and dried, and trace it to its termination in the ultimate air- 

 tubes or cavities, by carefully removing the portions of lung which are 

 upon it, and then the other half of its wall, so as to lay bare its interior, 

 we adopt, I believe, the best plan of ascertaining how the tube itself ter- 

 minates, in what manner the air cavities proceed from it, and what rela- 

 tion they bear to it. For this purpose, we should expose a bronchial 

 tube, from its entrance into a lobule, to its termination. We find that 

 the bronchial tube, having entered its lobule, divides and gives off 

 branches, and at last terminates in a dilatation, which has opening into 

 it a number of orifices. These orifices lead to a number of canals, which 

 have been variously designated : ' intra-lobular bronchial ramifications' 

 (Addison, PhilosopTiical Transactions, 1842); ' lobular passages' (Todd 

 and Bowman, v. ii. p. 390); 'intercellular passages' (Rainey on the 



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