DEPARTMENT OF EMBRYOLOGY.* 



George L. Streeter, Director. 



As has been our experience in previous years, the work of this depart- 

 ment during the past year approaches our primary problem — human 

 embryology — from several directions. It includes the microscopic 

 structure of the individual cell and the grosser anatomy of organ 

 systems in their different stages, as well as the body as a whole. 

 Furthermore, our studies not only concern the morphology of normal 

 human embryos, but it has also been found necessary to consider the 

 abnormal and the factors involved in their causation. To some extent 

 we have resorted to other animal forms in which experimental pro- 

 cedures are possible and have found the element of control introduced 

 by experiment to be of very great assistance. In the following report 

 these various studies will be grouped for greater convenience under 

 three general headings: those concerning the structure of the cell, or 

 cytology, those concerning the development and structure of individual 

 organ systems, and finally, the clinical and pathological studies bearing 

 on the abnormal development of the embryo. Before the description 

 of the character and results of these studies is entered upon, mention 

 may be made of two events in the further progress of the development 

 of our organization. 



Since 1915 our researches have been conducted in a suite of rooms in 

 the Hunterian Laboratory of the Johns Hopkins University. These 

 quarters, while well adapted to our purposes, are limited in space, and 

 the extent of their capacity, as regards the housing and preparation of 

 the rapidly growing collection, has already been reached. To meet our 

 future needs a piece of property at the corner of Wolfe and Monument 

 streets, suitable for a building-site, has been deeded to the Carnegie 

 Institution of Washington by the trustees of the Johns Hopkins Uni- 

 versity, and the preliminary plans have been drawn for a four-story 

 laboratory building 100 by 50 feet. 



An important addition to our staff has been made by securing the 

 services of Dr. Warren H. Lewis, professor of physiological anatomy at 

 the Johns Hopkins University. His appointment as research associate 

 was made on August 1. The work of Professor Lewis has been devoted 

 mainly to problems in morphological and experimental embryology, 

 in which fields his contributions are w^ell known. Recently, in con- 

 junction with Mrs. Lewis, he has improved the methods of cultivating 

 embryonic tissues in artificial media, thus making it possible to follow 

 the differentiation of growing tissues under the microscope. This 

 procedure in their hands is yielding conspicuous results in the advance- 



♦Address Hunterian Laboratory, Johns Hopkins Medical School, Baltimore, Maryland. 



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