294: A Study of the Structural Unit of the Liver 
not yet been determined, but it is certain that in the cat and the dog 
they do not extend beyond the center of the portal unit. I have been able 
to trace them in numerous specimens beyond portal vessels .06 mm. in 
diameter, and this naturally puts them into the center of the unit. One 
great obstacle in the way of studying the finer lymphatics is that the 
amount of connective tissue and the size of the portal vein seem ‘to vary in 
inverse ratio, and when the veins of the sixth order are distended to their 
maximum the surrounding connective tissue is compressed, and conse- 
quently the lymph ducts are completely obliterated. It is not easy, there- 
fore, to obtain clear pictures of the lymphatics from their very beginning 
down to the main trunks. 
The origin of the lymphatics of the liver was first definitely determined 
by MacGillavry,” who studied this subject under the direction of Lud- 
wig. Long before the work of MacGillavry it had been observed that 
ligature of the bile duct was followed by passage of bile over into the 
lymphatics, and the artificial fillmg of the lymphatics naturally followed, 
by injecting a colored fluid into the bile duct. Sections of liver, in which 
the lymphatics had been filled with Prussian blue, or with asphalt, showed 
that the fluid injected into the bile ducts leaves them at the periphery of 
the lobule to enter spaces surrounding the blood capillaries, the so-called 
perivascular lymph spaces. These spaces communicate at the periphery 
of the lobule, that is, in the center of the portal unit, directly with the 
interlobular lymph channels. Frequently there is an extravasation of 
the injection mass into the blood capillaries of the lobule. 
These observations were subsequently confirmed by numerous compe- 
tent investigators, using the method employed by MacGillavry as well as 
that of direct injection of Prussian blue into the walls of the portal and 
hepatic veins. In successful injections made in this way it is found that 
the Prussian blue injected enters the center of the portal unit and from 
there radiates and encircles its blood capillaries.” Such injections, how- 
ever, are always accompanied with numerous extravasations of the 1m- 
jected material into the surrounding tissues, and often there is a secondary 
injection into the blood capillaries. This fact has raised an objection to 
the direct injection of the lymphatics from the bile capillaries. It ap- 
pears more probable, the opponents say, that the extravasation of bile, or 
the injected material into the center of the portal unit enters the lym- 
phatic radicals of the capsule of Glisson, and from them the larger lymph 
channels and the perivascular spaces of the capillaries are filled. Fur- 
3° MacGillavry, Wiener Sitzungsber., 1864. 
* Budge, Ludwig’s Arbeiten, 1875. 
