THE DEVELOPMENT OF THE CLOACA IN HUMAN 



EMBRYOS 



AUGUSTUS G. POHLMAN 

 Indiana University 



From the Anatomical Laboratory, Johns Hopkins University 



SEVEN FIGURES 



CONTENTS 



Introduction 1 



Material 7 



The cloacal membrane 13 



The ectodermal cloaca 15 



The tail gut 15 



The cloaca 16 



The division of the cloaca 17 



Summary 20 



Bibliography 22 



INTRODUCTION 



The active work in the embryology of the urogenital system 

 began about 1880 and continued for a period of some fifteen years 

 when Keibel's monograph was published. The writer's investi- 

 gation of the cloacal region was started in 1903, and was under- 

 taken in part as a control of Keibel's work, and in part with a 

 view toward solving some of the points on which differences in 

 opinion existed. The publication of this report has been delayed 

 in the hope that certain facts in comparative embryology might 

 be established and help to clarify some of the obscure relations 

 found in the human embryo. Inasmuch as the extensive investi- 

 gations of Fleischmann and his students have come to naught 

 in this respect, the major differences in opinion will be considered, 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 12, NO. 1 

 JULY, 1911 



1 



