Development of the Jugular Lymph Sacs. 307 
IV. GENERAL CONSIDERATIONS AND CONCLUSIONS 
In the preceding pages the writers have presented a detailed 
account of the development of the jugular lymph sacs in the 
domestic cat (Felis domestica). 
The primary principles underlying the development of the jugu- 
lar lymph sac are: (1) the development of a secondary channel 
parallel to the embryonic precardinal and the Cuvierian end of 
the postcardinal; (2) the association with this secondary channel 
of a certain number of dorsal precardinal tributaries, and (3) the 
separation of these two sets of venous elements, which we have 
termed ‘Veno-lymphatics’, from the main venous channels, and 
their subsequent conversion into the definite jugular lymph sacs 
by a process of growth and fusion. 
For a complete and short résumé of the development of the 
jugular lymph sac, illustrated by diagrams (figs. 8 to 21), the 
reader is referred to the topic in the preceding pages, entitled 
‘Analysis of Developmental Stages in the Formation of the 
Jugular Lymph Saes’ (page 202). <A short résumé, although 
less complete than the one referred to, was published in the Ana- 
tomical Record, Vol. II, 1908, to which the reader is also referred. 
The writers wish to make it perfectly clear that the present 
communication deals solely with the anatomy and development of 
the JuGuLAR LympH Sacs of the cat, and does not touch on the 
question of the origin of the independently formed systemic lym- 
phatic vessels which unite with the jugular sacs. 
Accepted by the Wistar Institute of Anatomy and Biology, December 2Ist, 1909. Printed May 
25th, 1910. 
