483 



Guido Fischer ('05) likewise figures the recurrent bronchi of 

 several of the air-sacs. The only reference he makes to these features 

 of his celloidin corrosion preparations, however, is in a note of explanation 

 of one of his figures in which he calls attention to a bronchial trunk 

 larger than the others in the network of air-tubes which extends to 

 the dorsal surface of the lung on its lateral side. This bronchial trunk, 

 he says, "directs itself toward'' the abdominal air-sac. 



It remained for Juillet ('H) to interpret and point out the 

 relationships of these important features of the avian lung. Juillet 

 found recurrent bronchi in all of the fourteen species of birds which 

 he examined. By a study of sections he traced some of the stages 

 of their development in the embryonic lungs of the chick and although 

 he does not give an extended account of their developmented history, 

 he arrived at a true conception of their nature. 



Technique: It would have been impossible to work out with any 

 degree of satisfaction the development of the bronchial tree and of 

 the recurrent bronchi without the use of a method originated by 

 HocHSTETTER of usiug clovc oil and chloroform. (Zeit. f. wiss. Mikr. 

 und mikr. Tech. Bd. XY, 1898). This method I modified by using 

 cedar oil instead of clove oil which 1 found to give clearer prepara- 

 tions and of longer duration. 



The lungs and air-sacs were dissected out of the previously fixed 

 and hardened specimens, then cleared in cedar oil, after which the 

 organs were placed in a mixture of one part cedar oil and two parts 

 chloroform. On becoming permeated with this fluid the preparation 

 was removed from the mixture and placed on a filter paper until the 

 chloroform might evaporate. The evaporation of the latter substance 

 served to draw the cedar oil from the lumina of the various branches 

 of the bronchial tree into the lung tissue and to fill the spaces thus 

 made with air. When the preparation was replaced in pure cedar oil 

 it gave every appearance of a metallic cast and the minute air pas- 

 sages that could not be injected by other means were made clear. 



The Seventh Day Stage. 

 There are five air-sacs in the lung of the adult fowl, and, as 

 I shall show later, one of these (sub-bronchial) is the result of the 

 fusion of two moieties that arise independently. The names employed 

 in the following descriptions are : prebronchial, sub-bronchial, anterior 

 intermediate, posterior intermediate, and abdominal air-sac. 



31* 



