ORGANS OF THE BODY. 415 



lymph-tubes (the lymph-passages of the medullary portion. Throughout 

 this extremely complicated cavity in the larger lymph-glands, then, a net- 

 work of fibrous bands and cells extends, springing from the lymphoid 

 substance on the one hand, and is attached to the septa on the other, 

 holding the whole lymphoid sustentacular matter in a tense condition. 



We must now turn to the more active portions of our organ, namely, 

 the blood and lymph streams. 



225. 



Artificial injection of the blood-vessels of lymph-nodes is a matter of 

 but slight difficulty. It shows us that the organs in question receive 

 their supply of blood from two different sources of unequal importance. 

 The larger arterial twigs in the first place pass into the septa and glandular 

 tissue through the hilus without exception, while the smaller branches 

 penetrate through the capsule into the interior. The last mode of supply, 

 however, is probably not always present, though others are wrong who 

 assert that it does not exist at all. 



Passing through the hilus in the first place then, one or several 

 small arterial trunks are seen which give off their first branches while 

 within the connective-tissue situated here. With the connective-tissue 

 a small number of these branches pass into the system of septa within, 

 ramifying with further division towards the periphery. Most of the 

 arterial twigs, however, penetrate into the lymph-tubes of the medullary 

 substance, and pursue their way within the offsets of the latter. Among 

 the smaller lyniph-tubes, such as those of the pancreas Asettii of the 

 rabbit and Guinea pig, as well as the mesenteric glands of man, each of the 

 former contains, as a rule, but one single axial vessel, either a small artery 

 vein or capillary. In lymph-tubes of greater diameter several of these 

 may be met with, or, as is the case in the inguinal glands of man and 

 lymph-nodes of the ox, these elements of the medullary substance contain 

 within them a thick arterial or venous axial vessel, and a long-meshed 

 capillary network around it (fig. 406), whose tubules have a medium 

 diameter of Q'0046-0'0090 mm., and form a most delicate interlacement 

 about the central vessel. Passing from the more external lymph-tubes, 

 these twigs, together with their capillaries, enter the follicles, and occupy 

 a considerable portion of its space, terminating eventually in a very loose 

 and rather irregular capjllary network. The latter exhibits at the periphery 

 of the follicle where it is most highly developed as a rule, numbers of 

 loops on the tubes from the union of which the venous radicals take 

 their origin, which lie more internally. These, on leaving the follicles, 

 penetrate into the lymph-tubes, and return (imitating the arrangement of 

 the arteries) through these to the hilus. 



The second source of supply of blood is the capsule of the lymph-node 

 which is traversed by arterial venous and capillary vessels. The first of 

 these appear in the bases of the interfollicular partitions as horizontal 

 twigs, which divide finally into finer branches encircling the various 

 follicles. The veins of the capsular tissue have a similar course. 



Internally the greater number of these capsular vessels sink into the 

 septa, communicating there with others coming from the hilus. 



Other twigs (rarely arterial or venous, but usually capillary) enter 

 the follicular tissue itself, taking a course through the stronger retinacula 

 of the investing space or through the partitions. 



We shall find later on that other organs, such as the spleen, liver, and 



