TRANSUDATION THROUGH ANIMAL TISSUES. 359 



medullary cords and immediately surrounding the trabeculae, constitute 

 the lymph-paths, or the channels by which the lymph traverses the glan- 

 dular substance from the afferent to the efferent vessels. The afferent 

 lymphatic vessels, according to the united testimony of more recent 

 observers, after ramifying upon the outer surface of the gland, penetrate 

 its fibrous envelope and become continuous with the transparent por- 

 tions of the glandular substance. This has been shown by injections of 

 the lymphatic gland from the afferent vessels ; and Kolliker has also 

 demonstrated a similar connection of the same channels with the efferent 

 vessels, by injecting these vessels from the substance of the gland. 



The lymph-paths present a transparent appearance in thin sections of 

 the gland for the reason that the granular lymph-cells which they con- 

 tain are easily detached and removed by manipulation, while those of 

 the medullary cords are more firmly fixed in the fibrous mesh-work and 

 do not readily yield to a displacing force. It has been found b/Kolliker 

 that a watery or serous fluid, injected through the substance of the gland 

 under very moderate pressure, will also displace these cells and leave 

 the spaces which they occupied nearly clear. For these reasons it is 

 regarded as certain that the lighter spaces in the lymphatic glands are, 

 as their name indicates, the channels by which the lymph passes from 

 the afferent to the efferent vessels, and that the lymph-cells are detached 

 by this current from the place of their growth and carried onward 

 through the rest of the lymphatic system. 



Translation and Absorption fcy the Animal Tissues. 



During the passage of the blood through the capillary bloodvessels 

 a variety of actions take place by which some of its ingredients are 

 given up to the tissues by transudation and are at the same time replaced 

 by others derived by absorption from the adjacent parts. The lym- 

 phatic system of vessels, furthermore, is entirely filled by the absorption 

 of materials taken up from the surrounding tissues ; and the composi- 

 tion of the fluid which they contain depends upon the property, belong- 

 ing to animal membranes, of transmitting or absorbing certain fluid 

 substances in a peculiar way. This property is exhibited experiment- 

 ally in the following manner. 



If a fresh animal membrane be firmly attached over the mouth of a 

 cylindrical glass tube, filled with pure water and immersed in solutions 

 of various substances, in such a manner that the membrane forms a 

 continuous diaphragm, having the water on one side and the solution 

 on the other, it is found that different substances penetrate the mem- 

 brane and pass through it to the water with very different degrees 

 of rapidity. As a general rule crystallizable substances, such as 

 mineral salts, glucose, urea, pass with facility ; while the non-crystal- 

 lizable organic matters, such as albumen, starch, gum, pass with com- 

 parative difficulty There are certain exceptions, however, to this rule. 

 Thus albumen, under ordinary circumstances, transudes slowly or not 

 at all through animal membranes ; while albuminose, which is also non- 



