Herbert M. Evans 197 
so few and consequently large, that they afford a particularly favorable 
opportunity to study the lymphatic vasa vasorum. One is surprised to 
see how profuse a blood-vascular net is closely embedded in the walls of 
these thin and delicate tubes. ) 
METHODS. 
In this study only those injections were used which had been long 
continued at low pressure. Carmine-gelatine was employed and was made 
up in general, according to the method given by Walker.’ With such 
injections the capillary bed was entirely filled. In one case, ultramarine- 
blue was afterwards injected into the vein. The superior mesenteric 
trunks were invariably taken and their colic and ileo-colic branches, care- 
fully ligated. The tissue was secured from one to five hours after death. 
After sufficient time in 95 per cent alcohol, the mesentery was examined 
in comparatively large pieces under the binocular microscope. Areas 
including lymphatic vessels of interest were generally cleared in creosote 
and mounted in toto on large glass slides in balsam or damar. It was 
usually necessary to carefully dissect out the larger ducts after they were 
cleared, for they are often surrounded by masses of fat, even in mesen- 
teries where fat is slight. The binocular enabled the most delicate dissec- 
tions to be made. Other ducts were embedded in paraffine and sectioned 
serially at 10 and 20 microns, to show the histology of the lacteal walls. 
The lymphatics of the intestine itself were studied by stripping off the 
serosa with the subjacent muscularis and by dissection of the sub-mucosal 
tunic. All drawings were done under the camera lucida and are thus 
as exact representations as I could secure. 
OBSERVATIONS. 
It is remarkable how small a lymphatic vessel may yet have some 
appreciable special blood-supply. Dogiel was led to believe that the 
“retaining” capillary net which he had seen was present along the lym- 
phatic vessel until the lymph capillaries were reached. JI am unable 
to verify this statement but it will serve to call attention to the decided 
smallness which the lymphatic channel may reach and still be supplied by 
blood capillaries. 
In the case of vessels somewhat larger than lymphatic capillaries, the 
lacteal is usually supplied by a single accompanying capillary and in 
‘Walker, G., The Blood-Vessels of the Prostate Gland. Amer. Jour. of 
Anat., Vol. V, No. 1, pp. 73-78, December, 1905. 
