ELABORATION OF NUTRIENT MATERIALS PEYER's GLANDS. 209 



though partly also through the interstices of the tissue forming the medul- 

 lary portion of the gland, where it comes into intimate relation with the 

 bloodvessels, and takes up a certain proportion of lymph-corpuscles. Wln-n, 

 however, the activity of the gland is at its height, as regards both the circu- 

 lation of the blood and that of the lymph, as af'te^ 1 food, the pressure of the 

 increased quantity of the lymph effects the dilatation of the minute pores, 

 by which the spaces between the connective-tissue corpuscles and their pro- 

 longations communicate with the alveolar investing spaces. A much more 

 rapid percolation of the newly-absorbed fluid is thus permitted through 

 channels in which lymph-corpuscles are abundantly contained, effecting 

 the first steps in its assimilation to that fluid, into which it is subsequently 

 poured, and of which it is obvious that it constitutes the pabulum. Oidt- 

 mauu analyzed a lymphatic gland from the inguinal region of an old woman 

 and found it to consist of water 71.5, and solids 28.5, of which last 1.2 parts 

 were salts. 



1-10. In immediate connection with the lymphatics are the large sacs or 

 cavities known as the Serous membranes, which, as the researches of Klein 1 

 have shown, may be regarded as lymphatic glands that have been unravelled 

 or opened out, and which present many points of interest in reference to the 

 processes of sanguification. The serous membranes, typical examples of 

 which are presented by the Pleura, Peritoneum, Pericardium, and Arach- 

 noid, as well as by the synovial membranes of joints, are composed of a 

 matrix of connective tissue, lined by a single layer of cells termed the endo- 

 thelium. They form closed sacs, existing between parts that are subject to 

 friction, the movements of which they facilitate by the extreme smoothness 

 and lubricity of their surfaces. The eudothelium for the most part consists 

 of a layer of flattened nucleated hyaline cell-plates, the sinuous outlines of 

 which can be brought beautifully into view by staining with nitrate of silver. 

 In many places, however, the cells present a different character, being poly- 

 hedral, club-shaped, or even short-columnar with granular contents and 

 ovoid nucleus, which is often constricted or divided into two. These germin- 

 ating or young eudothelial cells sometimes form projecting and pedunculated 

 masses, and some of them, closely resembling lymph-corpuscles, may be seen 

 either simply attached to the general surface, in the act of separating from 

 it, or actually free in the cavity of the membrane. The matrix of the serous 

 membranes, best seen in such a part as the omentum, is composed of a homo- 

 geneous substance, in which are imbedded cells of various kinds. These 

 according to their form and arrangement present (in the omeutum of the 

 rabbit for example) two kinds of lymphaugeal structures. In one there are 

 patches of more or less flattened branched cells lying in the lymph-canalic- 

 ular system, multiplying by division and growing up into lymphoid cells, 

 which are also contained in the lymph-canalicular system. In the second 

 kind there are patches and tracts, the matrix of which consists of a re- 

 ticulum, containing in its meshes a variable number of lymphoid corpuscles. 

 These patches are usually vascularized, but the former do. not originally 

 contain bloodvessels, though they subsequently become highly vascular ; by 

 coalescence they ultimately form large tracts. It is thus apparent that there 

 is a considerable amount of adenoid tissue imbedded in, or rather forming 

 the walls of, the serous membranes. The proper lymphatics of the serous 

 membrane form wide vessels, partly accompanying and sometimes invagiu- 

 atiug or surrounding, and partly running independently of the bloodvessels, 

 the walls of which consists of only one layer of fusiform eudothelial plates. 

 The larger ones have valves and sacculated dilatations. The existence of 



1 The Anatomy of the Lymphatic System. I. The Serous Membranes. 1873. 



