Herbert M. Evans 205 
external to the lymphatic wal] that it well might suggest a “ retaining 
net.” The capillaries, however, are closely bound to the lymphatic, as will 
be mentioned when the structure of the lacteal wall is considered, and 
as can easily be seen by attempted dissection under the binocular. The 
net which supplies the Impyhatics is never the only one which arises from 
the long-accompanying vessels, for these always supply the mesentery in 
the region where they course. This is well seen in the lacteal shown in 
Fig. 10, with the mesentery attached. Delamere,’ in speaking of the 
supra-valvular enlargements in the lymphatic vessels homologizes them 
Fie. 11. Showing unilateral blood-supply of one of the larger. collecting 
lacteals. X 50. 
with the true contractile sacs in some vertebrates. No very noticeable 
increase of muscle tissue can always be demonstrated here, nor is there 
usually much increase in the closeness of the vascular net supplying 
these areas. Fig. 10 gives the common appearance of the vasa vasorum 
in the neighborhood of the valves. It will be noticed that the long- 
accompanying vessels send strong cross branches just below the valves. 
This is by no means an invariable plan but I have found that, on the 
whole, such cross branches are commoner here than elsewhere. 
The larger collecting lymphatics of the human mesentery show little 
or no change in the essential plan of blood-supply. Here, too, accompany- 
7 Poirier and Charpey, ‘“ A Treatise of Human Anatomy ’—The Lymphatics 
—General Anatomy, by G. Delamere. English Ed. Trans. by C. H. Leaf, 
Chicago, 1904. 
