452 WILLIAM A. LOCY AND OLOF LARSELL 



Wood's metal and Darcet's metal besides plastic reconstructions 

 and the usual embryological and histological methods. An ade- 

 quate review of this excellent paper would require much space 

 and it should be read in the original. Our observations differ in 

 some particulars from those of Juillet (especially as regards the 

 origin of the interclavicular air-sac) and these differences will be 

 commented on later. 



Technique. Chick embryos from the close of the second day 

 up to the time of hatching were used in observations on the de- 

 veloping lung. The stages were compared with the figures in 

 Duval's Atlas d'Embryologie and his chronology adopted. 



For dissecting, fresh embryos were first immersed in a solution 

 of 8 per cent formalin and preserved in a 4 per cent solution. 

 While the heart was still pulsating a large number of the embryos 

 for dissection were injected with India ink through the vascular 

 area or the liver according to the age of the embryo. Dissec- 

 tions were made of stages from three days to hatching, of young 

 chicks one, two and three days after hatching and of adults. 



For imbedding, the embryos were fixed in Kleinenberg's picro- 

 sulphuric solution and in formalin. Stages from 48 to 96 hours 

 were sectioned from eight to ten microns in thickness and sections 

 were also made of older stages and of the lung parenchyma of 

 the adult. 



It would have been impossible to work out with any degree of 

 satisfaction the development of the bronchial tree and of the re- 

 current bronchi without the use of a method originated by Hoch- 

 stetter (Zeitschr. fiir Wissenchft, Mikr. und Mikr. Tech., Bd. 

 XV, '98) of using clove oil and chloroform. This method was 

 modified by using rather thick cedar oil instead of clove oil which 

 was found to give clearer preparations and those of longer dura- 

 tion. 



In stages subsequent to 90 hours, 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 re- 

 moved from the mixture and placed on a filter paper until the 



