432 ABSORPTION. 



The peculiarities which the lymphatics present in the 

 different tissues and organs do not possess much physiolo- 

 gical interest, except the arrangement of the vessels of ori- 

 gin in the substance of the brain and spinal cord. In the 

 skin, the only interesting peculiarity which we have not al- 

 ready noticed is that the vessels appear to be very unequally 

 distributed in different parts of the surface. According to 

 Sappey, 1 they are particularly abundant in the scalp over the 

 biparietal suture, the soles of the feet and the palms of the 

 hand, the fingers at the lateral portion of the last phalanges, 

 and the scrotum. In the median portion of the scrotum, they 

 attain their highest degree of development. They are also 

 found, though in fewer numbers, originating from around 

 the median line on the anterior and posterior surface of 

 the trunk ; the posterior median portion of the extremities ; 

 the skin over the mammae ; and around the orifices of the 

 mucous passages. Sappey has injected lymphatic vessels in 

 the anterior portion of the fore-arm, the thigh, and the leg, 

 and the middle portion of the face, though they are demon- 

 strated with difficulty in these situations. If they exist at 

 all in other portions of the cutaneous surface, they are few in 

 number and rudimentary. 



In the mucous system, the lymphatics are very abundant. 

 Here are found, as in the skin, two distinct layers which en- 

 close between them the whole thickness of the mucous mem- 

 brane. The more superficial of these layers is composed of 

 a rich plexus of small vessels, and beneath the mucous mem- 

 brane is a plexus consisting of vessels of larger size and less 

 numerous. The superficial plexus is exceedingly rich in the 

 mixed structure which forms the lips and the glans penis, and 

 around the orifices of the mouth, the nares, the- vagina, and 

 the anus. There are certain mucous membranes in which the 

 lymphatics have never been injected. These are the mucous 

 membrane of the bronchial tubes, the membrane lining all 

 of the ducts of the glands except the ureters, the Schneide- 



1 Op. dt. 



