THE DEVELOPMENT OF THE THORACIC DUCT IN 



THE PIG 



OTTO F. KAMPMEIER 

 Fro?n the Laboratory of Comparative Anatomy, Princeton University 



THIRTY-FIVE FIGURES (FIVE COLORED PLATES) 1 



I. INTRODUCTION 



At the present day the question of the origin of lymphatics has 

 become one of the most interesting problems and is holding the 

 attention of perhaps as great a number of investigators as any 

 other problem in the field of embryology and anatomy. This is 

 partly due to the fact that the lymphatic system as a whole is 

 the last of the organ-systems to be taken up for more thorough 

 investigation, and partly it is the result of the impetus given by 

 modern physiology which has emphasized the question of the 

 relationship between lymphatics and blood vessels and their func- 

 tional significance in the economy of the organism. Although this 

 problem has been attacked at various times in the history of 

 anatomy, relatively few important advances have been made, 

 and it is only recently during the last decade that it has been 

 attacked with renewed vigor and has been pushed to the critical 

 point of its solution. The question of the individuality of a 

 lymphatic, especially, has developed a most animated contro- 

 versy between two schools diametrically opposed in their conten- 

 tions. One of these maintains that all lymphatic channels are 

 a direct product of the venous system, and the other that they 

 arise independently of it, and that if they do enter into certain 

 structural venous relations during their genesis such relations are 

 purely of a secondary character. 



1 Expense of illustrations partly borne by author. 



401 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 13, NO. 4 



