THE PHARYNGEAL POUCHES AXD THEIE DERIVATIVES 

 IN THE MAMMALIA. 



BY 



HENRY FOX, Ph.D. 



With 73 Figures. 



The present paper is an outgrowth of an earlier unpublished article 

 submitted to the Faculty of the University of Pennsylvania in partial 

 fulfilment of the requirements for the degree of Ph.D. The original 

 article gave the results of a study of six or seven different stages in the 

 development of the pig. Subsequently, through the kindness of Dr. 

 C. S. Minot, I was enabled to study the extensive series of mammalian 

 embryos in the collection of the Harvard Medical School. Of these I 

 studied most thoroughly the series of pigs and cats, but also gave some 

 attention to the later stages in the rabbit. The results of this addi- 

 tional study, along with those included in my former article, I noAV 

 offer in the present paper. 



My aim is to give a complete history of the pharnygeal pouches and 

 their derivatives as typically exemplified in the mammalia. The main 

 facts of this history had been largely determined previous to my start- 

 ing the investigation, but the interpretations attached to these facts by 

 various authors differed considerably, and, moreover, there remained 

 a number of details about which there was much confusion. These 

 unsettled matters seemed to me to warrant a full investigation of the 

 subject. 



Soon after I had begun my observations an important article by 

 Hammar appeared treating of the development of the fore-gut in man. 

 Hammar had in his possession a large series of embryos, and from 

 these he made out a full and consistent history of the middle ear and 

 Eustachian tube. He also compared with his own results the state- 

 ments made by earlier authors, and, through the more abundant 

 material at his command, was enabled to show how their conclusions 

 were in most cases the result of mistaken interpretation based on an 

 insufficient body of facts. 



The American- .Journal of Anatomy.— Vol. YIII, No. 3. 



