2 The Development of the Lungs 
of celluloid corrosions. For this purpose celluloid is dissolved in ace- 
tone and injected from aspiration bottles into the lungs through the 
trachea. Like the cellodin corrosions these were digested or macerated 
in concentrated hydrochloric acid. The advantage of celluloid over cel- 
loidin casts lies in the fact that the former, hke Wood’s metal, may be 
left in the air and handled freely without the disadvantages of the 
glycerine bath, which often makes it either difficult or impossible to 
study certain parts of the celloidin preparations. For the study of the 
development of the respiratory lobules a combination of celluloid and 
Wood’s metal preparations proved most advantageous. Preparations of 
the entire embryonic !ung cleared in oil of cloves were also found ser- 
viceable as control preparations for the reconstructions. They are, how- 
ever, of doubtful value save for this purpose as the young dorsal and 
ventral buds on the stem bronchus are almost invisible until they have 
reached a considerable size. 
The organogenesis was followed in a series of stained sections from 
embryos and lungs hardened in Zenker’s fluid and stained by Mallory’s 
method. At the period of birth the alveoli were distended by injecting 
them, under low pressure, with Zenker’s fluid, thus obviating the obscure 
and uncertain pictures which are obtained when the lung is collapsed 
and contracted. In following the development of the epithelium, the 
well-known silver nitrate method has been used. 
REVIEW OF THE LITERATURE. 
To von Baer, 28, we are indebted for the first description of the de- 
development of the pulmonary apparatus. In the chick it consists of two 
small hollow swellings about the middle of the head gut, which ap- 
pear on the third day. These projections give rise to the lungs, while 
the hollow cavities represent the rudiments of the bronchi although 
the trachea up to this time is unformed. On the fourth day the lungs, 
still in connection with the «esophagus, he more ventralwards, but the 
bronchi in growing backwards have dilated into small sacs. Anteriorly, 
however, the bronchi join each other at an acute angle and terminate in a 
short canal, the anlage of the trachea which communicates with the ceso- 
phagus behind the pharynx. These observations were amplified by the 
work of Remak, 55, Selenka, 66, Gotte, 67, and especially His, 68, who be- 
lieves the larynx and trachea arise from a ventral groove in the head gut. 
Caudalwards, this structure has two lateral projections representing the 
rudiments of the bronchi which are bilateral and paired in contra- 
distinction to the unpaired anlage of the larynx and trachea. Less in 
