THE TERMIN AL LYMPH VESSELS. S61 
(1) The skeleton or framework consists of a capsule and of primary, secondary, and tertiary 
trabeculae. 
The capsule is formed of white fibrous tissue interspersed with elastic fibres, and in some cases 
with unstriped muscular fibres. 
The primary trabecule spring from the deep surface of the capsule and radiate towards the 
hilus, where they anastomose together and become again continuous with the capsule; they 
divide the interior of the gland into lobes. Where they spring from the capsule they are 
flattened, but as they approach the centre of the gland they become rounded ; their structure is 
the same as that of the capsule, and from their surfaces the secondary trabecule are given off. 
The secondary trabecule, springing from the surfaces of the primary trabecule, cross the 
lymph sinuses and enter the lymph cords and follicles, where they terminate by dividing into 
tertiary trabeculae. As they cross the lymph sinuses they anastomose freely together, forming a 
fine mesh-work through which the lymph passes in its course from the afferent to the efferent 
vessels. The secondary trabecule consist of fine strands of fibrous tissue devoid of nuclei, and 
their surfaces are covered with endothelial cells) The tertiary trabeculw are finer and more 
delicate than the secondary trabeculie, from the terminations of which they spring, but they 
have a similar structure. They anastomose together, forming a fine network in the lymph cords 
and follicles, and the spaces of the network are filled with lymph corpuscles. 
(2) The lymph sinuses lie beneath the capsule and around the primary trabeculee which 
form their boundaries on one side, whilst on the other they are limited by the lymph cords 
and follicles. They are traversed by the secondary trabeculee, and their channels are thus 
converted into a kind of sponge-work through which the lymph stream flows. In the peripheral 
or cortical parts (substantia corticalis) of the glands they form more or less cylindrical channels, 
but towards the central or medullary parts (substantia medullaris) and near the hilus they 
become moniliform. Afferent vessels (vasa afferentia) enter the sinuses which he immediately 
beneath the capsule at various points, whilst the efferent vessels (vasa efferentia) emerge close 
together at the hilus. 
(3) The lymph follicles and cords are interposed between the lymph sinuses. They consist 
of dense masses of lymphoid cells embedded in a stroma formed by the tertiary trabecule. The 
follicles and cords are quite similar in structure, but the follicles are large masses which inter- 
vene between the sinuses in the cortex of the gland, and the cords are rounded and irregular 
strands which lie between the moniliform sinuses of the medullary portion. 
It is generally believed that the lymph corpuscles in the follicles and cords are white blood 
corpuscles undergoing proliferation. If this belief is well founded, lymph glands must be looked 
upon as one of the sources from which white corpuscles are derived. 
The lymph glands are embedded in the connective tissues, some lying super- 
ficially in the subcutaneous tissues, but the majority more deeply and usually at 
the sides of the great blood-vessels. As a rule they are arranged in groups of 
from two to fifteen, but a few of those which le in the subcutaneous tissues are 
solitary. 
They form centres to which afferent lymphatic vessels converge, and from 
which efferent vessels pass onwards to the larger lymph channels. 
The student should therefore acquaint himself with the various groups of 
glands, with their afferents and efferents, and with the exact position and relations 
of the large lymphatic trunks; he will then be in a position to understand the 
course which minute organisms or particles, which have gained access to the lymph 
spaces, may take as they are carried in the lymph stream, and he will realise that 
such structures may either be entangled in the glands through which the lymph 
passes, or, having escaped all obstructions, that they will finally enter the veins at 
the root of the neck. At the same time,if he bears in mind the existence of 
the numerous anastomoses between the lymphatic vessels, he will have no difticulty 
in appreciating that variations from any regular course may not infrequently 
oceur, and his clinical experience at a later period will show that such variations 
are by no means Uncommon. 
THE TERMINAL LYMPH VESSELS. 
The terminal lymph vessels are the thoracic duct and the right lymphatic duct. 
Thoracic Duct.—The thoracic duct (ductus thoracicus) is the larger and 
the longer of the two terminal lymph vessels. It commences in the umbilical 
region of the abdomen as an elongated ovoid dilation—the receptaculum chyli 
(cisterna chyli)—which measures 6 to 8 mm. (4 to ¢ in,) in its broadest diameter, 
and from 5 to 7-5 em. (2 to 5 in.) in length. The receptaculum chyli les between 
the aorta and the lower part of the vena azygos major, under cover of the right crus 
of the diaphragm, and opposite the first and second lumbar vertebree. Passing 
