Bibliography of the Venous System.
(498) J. Marshall. “On the development of the great anterior veins.” Phil. Trans., 1859.
(499) H. Rathke. “Ueb. d. Bildung d. Pfortader u. d. Lebervenen b. Säugethieren.” Meckel’s Archiv, 1830.
(500) H. Rathke. “Ueb. d. Bau u. d. Entwick. d. Venensystems d. Wirbelthiere.” Bericht. üb. d. naturh. Seminar. d. Univ. Königsberg, 1838.
Vide also Von Baer (No. [291]), Götte (No. [296]), Kölliker (No. [298]), and Rathke (Nos. [299], [300], and [301]).
The lymphatic system arises from spaces in the general parenchyma of the body, independent in their origin of the true body cavity, though communicating both with this cavity and with the vascular system.
In all the true Vertebrata certain parts of the system form definite trunks communicating with the venous system; and in the higher types the walls of the main lymphatic trunks become quite distinct.
But little is known with reference to the ontogeny of the lymphatic vessels, but they originate late in larval life, and have at first the form of simple intercellular spaces.
The lymphatic glands appear to originate from lymphatic plexuses, the cells of which produce lymph corpuscles. It is only in Birds and Mammals, and especially in the latter, that the lymphatic glands form definite structures.
The Spleen. The spleen, from its structure, must be classed with the lymphatic glands, though it has definite relations to the vascular system. It is developed in the mesoblast of the mesogastrium, usually about the same time and in close connection with the pancreas.
According to Müller and Peremeschko the mass of mesoblast which forms the spleen becomes early separated by a groove on the one side from the pancreas and on the other from the mesentery. Some of its cells become elongated, and send out processes which uniting with like processes from other cells form the trabecular system. From the remainder of the tissue are derived the cells of the spleen pulp, which frequently contain more than one nucleus. Especial accumulations of these cells take place at a later period to form the so-called Malpighian corpuscles of the spleen.
Bibliography of Spleen.