CHAPTER VTT 

 ABSORPTION 



Section i. 



Lymph. 



Lymph may be regarded as the material by which the tissues are 

 directly nourished, and by which effete material is collected from 

 them and taken back to the blood ; there are certain non-vascular 

 structures, such as the cornea, cartilage, etc., where the lymph 

 circulation is the only means by which the part is supplied with 

 nourishment. Speaking generally, the lymphatic system may 

 be described as the drainage system of the body, in contradistinc- 

 tion to the blood or irrigating system. Though the latter is not 

 exclusively devoted to irrigating, it may also take up material 

 from the tissue spaces. 



The Lymph Spaces. — The tissues are bathed in lymph, which 

 is contained in the lymphatic spaces existing between the capil- 

 lary bloodvessels and capillary lymph- vessels. There is a con- 

 stant passage of material from the blood into the tissues, from 

 the tissues into the lymph, and likewise from the tissues back 

 to the blood. 



The lymph spaces are irregular passages in the connective tissue, 

 the larger ones being lined by epithelioid plates of a peculiar 

 irregular outline ; these spaces exist outside the bloodvessels, and 

 the lymph finds its way from the bloodvessels into the lymph 

 spaces. From the lymph spaces the fluid reaches the lymph 

 capillaries, but the means by which it gets there is not clear, 

 for it appears certain that, excepting in a few cases, there is no 

 direct communication between the space and the capillary. In 

 the vessels of the brain a peculiar arrangement is present ; the 

 lymphatic vessel surrounds the artery, and obtains its lymph 

 direct ; these are known as perivascular lymphatics. The lining 

 of the Lymph Capillary is composed of the same epithelioid plates 

 with irregular outline which are found in the spaces, and it is 



264 



