LYMPHATIC SYSTEM. 619 



guiding the course of the contained lymph, and in prevent- 

 ing the flow of injected fluids against their natural direction. 

 The compact aggregate masses of convoluted lymphatic ca- 

 pillaries, forming the conglobate glands, so rarely met with 

 in lower vertebrata, are now general, distinct, large, and nu- 

 merous in the course of these vessels. They abound especially 

 in the inguinal and axillary regions, on the sides of the neck, 

 and along the course of all the great veins. The lymphatic gan- 

 glia of mammalia are common in the general cavities, and 

 around the great viscera of the pelvis, abdomen, and tho- 

 rax, and even in the interior of organs, as along the divi- 

 sions of the bronchi in the substance of the lungs. They are 

 commonly more concentrated, fewer, and larger in the infe- 

 rior quadrupeds than in man ; and from their deficiency in 

 the cranial cavity, where lymphatic vessels abound, their 

 office appears to be incompatible with the delicate functions 

 of the brain. They are often tinged by peculiar contents of 

 their vessels or by the colours of the surrounding parts, es- 

 pecially after death, as in the vicinity of the liver, the spleen, 

 and the bronchi, and they often acquire a cellular appear- 

 ance internally, as in the cetacea, from dilatations of their 

 minute convoluted tubes, or of their connecting cellular tis- 

 sue. Though they do not occur within the skull, the lym- 

 phatic glands are common on the exterior parts of the head, 

 as behind the ears, beneath the lower jaw, and on the in- 

 side of the parotids. 



The lymphatic vessels not only form integrant parts of all 

 the organs and tissues of the body, but by injection many 

 of them appear to be almost entirely composed of these ves- 

 sels. Though smaller in mammalia than in lower classes, 

 they are more numerous and more extensively distributed, 

 they are much larger than the capillary blood-vessels which 

 spread on their parietes, they are wider than the terminal 

 tubuli of most glands, and their minutest branches are per- 

 ceptible by the naked eye. Their subcutaneous layer now 

 forms a more compact and continuous stratum over all the 

 superficial parts of the body, as they appear also over all the 

 mucous and serous membranes of the interior, forming an 

 inextricable network as little provided with, and as little re- 

 quiring villous commencements or orifices as the sanguife- 

 rous capillaries they accompany, and in which the limpid, 



