ORGANS OF THE BODY. 427 



with another prolongation of the fibrous envelope of the spleen directed 

 inwards in the form of a system of septa. In the nature of the latter, as 

 regards the spleen of the several mammalian animals, extraordinary 

 variety has been observed. Just as was the case in the lymph nodes, it 

 is but very slightly developed in the spleen of smaller mammals, as, for 

 instance, in that of the mouse, the squirrel, the Guinea pig and rabbit, 

 while in larger animals, as in horses, pigs, sheep, and oxen, it attains a 

 high pitch of development. In man, and in the dog and cat, on the other 

 hand, it is but moderately marked, reminding us of the lymph nodes 

 again. The more numerous the trabeculse in any spleen the harder is the 

 organ found to be. 



From the whole internal surface of the fibrous envelope there spring a 

 multitude of fibrous cords and bands, varying as to their distance from 

 one another, and as to the angle at which they are given off. Their 

 diameter is about 0-1128-0-1279, or even 2*2556 mm. These trabeculoe of 

 the spleen traverse the organ in all directions, uniting and again branch- 

 ing in the most irregular manner. They form, when in a state of perfect 

 development, a very complicated sustentacular tissue. On the other side 

 they are connected with the sheaths of the vessels, or continuous with 

 the latter, especially the veins (Tomsa). 



Within the innumerable irregular spaces, formed by the intercom- 

 munication of these trabeculse, the glandular tissue of the spleen is con- 

 tained. When the system of septa is fully developed, therefore, the 

 spleen of the larger animals acquires necessarily a complexity of structure, 

 rendering the recognition of its nature of great difficulty. On this 

 account the spleen of smaller animals is the most suitable object for 

 investigation, as was also the case with the lymph nodes. 



In its more minute structure the tissue of the trabeculae resembles that 

 of the capsule. Here we find, again, a closely woven whitish connective- 

 tissue, with nuclei and elastic iibres ; in addition to these, also, longi- 

 tudinally arranged muscular elements. The latter present themselves, 

 either in all the septa, as in the case in the spleen of pigs, dogs, and cats 

 (Koelliker, Gray), or, as is stated by many, only in the smaller trabeculae. 

 Thus it is in the ox and sheep (Koelliker, Ecker, Billroth). In man the 

 number of muscle fibres is small. 



230. 



Now, in the cavities aiready described in the preceding section, amid 

 this system of trabeculae, the glandular or lymphoid portion of the gland 

 is contained. This consists, as we have already remarked, of a network 

 of cords or bands, the pulp tubes analogous to, but not identical with, the 

 lymph tubes of the medullary portion of the true lymphatic glands. In 

 this, and connected with it, a number of lymphoid follicles are imbedded, 

 discovered some centuries ago by Malpiglii, and named in honour of him 

 Malpighian corpuscles (Milzkorperchen, Milzblascheri). 



In many respects these are exceedingly like the follicles of lymphatic 

 glands. They are not, however, grouped peripherally to form, as in the 

 latter, a cortical portion, but occur scattered throughout the whole of the 

 pulp. Their relation and connection to the arterial part of the vascular 

 system is very peculiar, calling for a few moments' consideration. 



It is only rarely that, as among the ruminants, the splenic artery makes 

 its entry into the spleen as one single trunk: it generally divides into 

 several branches before doing so. Each of the latter then preserves in 



