= 
CC 
LYMPHATIC AND 
be said to receive the lymph of three-fourths of 
the body, together with the whole of the chyle. 
The right lymphatic trunk is about two lines 
in diameter, very short, corresponding in situa- 
tion and length to the last half-inch of the left 
trunk ; consequently it will only be found at 
the root of the neck, close to the point of its 
termination. This trunk receives the remaining 
fourth of the lymph, viz. that collected from the 
right upper fourth of the body. Professor 
Lippi published a work on the lymphatic 
system in the year 1825, in which he described 
in the human subject many terminations of the 
lymphatics in other parts of the venous sys- 
tem, especially in the vena cava inferior, the 
vena porte, and the principal branches by 
which these vessels are formed, but subsequent 
observers have not corroborated his views. The 
vessels which Professor Lippi saw joining 
_ other large venous trunks were evidently the 
returning veins of the conglobate glands, into 
which the injection received by the lymphatics 
had passed during its transit through the glands : 
—a fact of extreme interest, and to which we 
must recur in speaking of the structure of the 
glands, but which has been observed by every 
anatomist who has had much practical experi- 
ence in injecting the lymphatic system. Lippi 
would have been perfectly correct, how- 
ever, had he confined his statement to what 
takes place in Birds, Reptiles, and Fishes. 
The lymphatic vessels resemble the veins in 
possessing valves, and in conveying their 
contents from branch to trunk ; moreover their 
internal tunics are continuous where the one 
set of vessels joins the other. In their mode 
of distribution also throughout the body the 
analogy between the two systems is consi- 
derable. Eustachius, when he first saw the prin- 
cipal trunk of the lymphatics, from its being 
filled with chyle, at once described it under 
the name of the vena alba thoracis, and many 
have considered the lymphatic vessels as an 
appendage to the venous system, rendering it 
more perfect. Although we are warranted in 
saying that the lymphatic vessels convey their 
contents from branch to trunk, by which is 
generally understood from smaller and more 
numerous to larger and less numerous vessels, 
as is the case with the veins; yet is there~an- 
other principle apparently of an opposite kind 
observed in their distribution, by which the in- 
fluence of capillary attraction is engaged in the 
important service of moving onward their con- 
tents, at the same time that these are ex- 
posed to a larger surface of the containing 
vessels, from which in all probability they derive 
some essential modification. This admirable 
and simple provision is especially evident in 
the lower extremities, where the greatest resis- 
tance from gravity is to be overcome. A vessel 
on the instep, for instance, of half a line in 
diameter, instead of emptying itself into a 
larger one as it proceeds upwards, bifurcates 
into vessels of equal diameter with itself; each 
of these again will in a similar manner sub- 
divide, until at length bya series of dicho- 
tomous divisions, although some reunions may 
take place, this single vessel has multiplied 
LACTEAL SYSTEM. 207 
itself by the time it reaches the inguinal region 
into as many as fifteen or more branches, each 
of the same diameter or nearly so as the ori- 
ginal branch on the instep. Indeed, through- 
out the lymphatic system, we scarcely find a 
branch of more than an inch in length whese 
diameter is not within the range requisite for 
the production of capillary attraction. The 
thoracic duct itself, which is two or three lines 
in diameter, may be said to form an exception, 
but the onward progress of its contents is 
specially provided for by its juxta-position to 
the aorta, from which circumstance it is sub- 
jected during life to an alternating pressure of 
considerable force, and fully competent in a 
vessel provided with valves to ensure the ad- 
vance of its contents. 
The principal lymphatics in any part of the 
body may be said, taken collectively, to equal 
the capacity of the arteries or veins of the same 
part ; thus, in the inguinal region the sum of 
the diameters of the lymphatic vessels may 
equal the diameter of the main channel by 
which the venous blood is returned from the 
lower extremity ; but by this simple subdivision 
of the outlet for the lymph into numerous 
branches, that almost universal, and, in its 
effects, wonderful power, by which the nutrient 
fluid throughout the vegetable creation is car- 
ried from the lowest fibril of the root to the 
highest living point in vegetable existence, is 
made available in the progression of the lymph in 
animals towards the centres of the system. This 
disposition of the lymphatic vessels throughout 
their course necessitates a greater uniformity in 
point of size, than we find to hold good with 
the artery or vein, and indeed constitutes their 
chief peculiarity in distribution when com- 
pared with the other divisions of the vascular 
system. The arborescent appearance, except 
on the surface of the liver and spleen, is 
scarcely to be met with in the lymphatics ; they 
almost always form a net-work of vessels, the 
meshes of which vary both in form and size 
in the different organs and in different parts 
of the body; as a general rule, when the 
vessels have a short course to run, the spaces 
they enclose are small and more nearly equi- 
lateral; but when the contrary is the case, as 
occurs in the extremities, the meshes are very 
large and much elongated, so that the vessels 
run nearly parallel with each other, and the 
net-work arrangement is scarcely perceptible ; 
there is, however, still less appearance of arbor - 
escence. 
In this respect the lymphatics may be said 
to resemble more the capillary bloodvessels, 
which in the web of the frog’s foot, or in the 
vesicular lungs of the salamander, toad, or frog, 
are so plainly seen to form a net-work of nearly 
equal-sized vessels, and, indeed, to cease to be 
capillaries when they become arborescent. 
Another peculiarity in the disposition of the 
lymphatic vessels occurs at their approach to a 
conglobate gland, through which their contents 
‘are to be conveyed. The vessels leading to a 
gland which are termed the vasa inferentia or 
afferentia of the gland, vary in number, being 
seldom less than two, and rarely amounting to 
