On the development of the pulmonary circulation in the chick

Although the chick long ago achieved the position of a classic in embryological studies, certain crucial details in the establishment of its pulmonary circulation have been left in t,he greatest obscurity. The textbooks for many years have been giving accounts, adequate enough, of the origin of the pulmonary artery, but the development of the corresponding vein has for the most part been mentioned only incidentally in connection with hatching (Lillie). Even with respect to the arterial course in the lung proper, particularly its relation t o the capillary system, there remains doubt, for the exact time and mode of completion of this portion of the circuit has not been directly determined in the chick, nor for the most part as closely inferred from investigations on other forms as it might havebeen. It was for these reasons that I began an investigation of this subject at the suggestion and under the direction of Professor Otto C. GIaser.