18 DEVELOPMENT OF THE SYSTEMIC LYMPHATIC VESSELS 



CROWN RUMP CROWN ROMP 



These embryos are contained in the Embryological Collection 

 of Columbia University. The majority of the preparations were 

 fixed in Zenker's fluid and stained differentially on the slide 

 with Hsemotoxylon (Delafield) and Orange-G. 



I have also had, through the courtesy of Professor McClure, 

 the opportunity of carefully examining three very interesting 

 cat embryos of the Princeton Collection, series 34 and 37, each 

 of 14 mm. crown-rump measure, and series 53, a 15 mm. embryo. 



A series of 180 adult animals with successful injection of the 

 main systemic lymphatics served as control for the embryologi- 

 cal determinations, and for the comparison of normal and variant 

 adult conditions of the venous and lymphatic systems with the 

 corresponding ontogenetic stages. 



The results of my observations on the development of the 

 mammalian systemic lymphatic vessels, as distinguished from 

 the jugular lymph sacs, studied jointly with McClure, may be 

 briefly summed up as follows: 



The systemic lymphatic vessels of the entire body are formed 

 through confluence of numerous originally separate intercellular 

 mesodermal spaces, which develop 'in great part in close apposi- 

 tion to the walls of the embryonic venous channels, and in exactly 

 the same way as the primary anlages of the haemal vascular 

 system, but independent of the latter. The endothelium lining 

 these first anlages of the lymphatic vascular channels is from the 



