152 



ANIMAL PHYSIOLOGY. 



prevent the injection of fluid backwards from the larger 

 trunks into the radicles. These valves are set so thickly as 

 to give to the vessels, when filled, a 

 beaded appearance, there being a dila- 

 tation opposite each valvular pouch. 

 In the limbs and in the walls of the 

 trunk, they are arranged in a deep and 

 superficial set; and in the viscera 

 there is usually, in like manner, a set 

 on the surface of an organ, and a deep 

 set accompanying its blood-vessels. 



At different points in their course 

 the lymphatics are interrupted by 

 lymphatic glands, tough structures, 

 often about the size of an almond, and 

 mostly arranged in groups. Each of 

 these receives a number of lymphatics 

 distinguished as afferent vessels, which 

 pour their contents into it, and gives 

 off a number of efferent vessels which 

 carry the contents onwards. They 

 are liable to be swollen or inflamed by 

 the irritation of fluids brought to them 

 from inflamed parts, and in that state 

 are often felt through the skin as hard 

 knots, popularly known as kernels. 

 Thus, hardened kernels are often felt 

 in the neck after eruptions on the 

 head, and below and behind the jaw 

 after toothache; in the upper part of 

 the thigh, from blisters of the foot; 

 and in the armpit from irritations on 

 Fig. 80. LYMPHATIC the arm, back, or breast. 

 GLAND of the groin. m The i vmp h at i c s commence in 

 a, An afferent duct, n ,..,,.,., 



with the concavities ver 7 fine networks, and in interstitial 

 of the valves turned spaces in the tissues; in some instances 

 toward the gland ; b, lined with exceedingly delicate epi- 

 b efferent ducts with thelium, like the capillary blood-vessels, 

 the convexities ot i ,1 . mi ^ i i -i 



their valves toward and m others not - The flmd whlch 

 the gland (Mascagni). they contain is termed lymph. The 



