THE ABSORBENT SYSTEM. 



601 



The absorbents of the body generally, which always convey the 

 transparent lymph, and are named the lymphatics, commence, by net- 

 works, near the various membranous surfaces, and in the interior of 

 certain tissues and organs. Their number, in any part, seems to be 

 proportionate to the quantity of areolar tissue which it contains, 

 rather than to the number of its bloodvessels, or the activity of its 

 functions ; thus, lymphatics have not been found in the brain and 

 spinal cord, and only a few in the muscles ; but in the subcutaneous 

 areolar tissue, and the intercellular spaces, they are very abundant. 

 They are numerous in the serous and synovial membranes, but still 

 more so on the mucous membranes and skin. The trunks from the 

 commencing lymphatic networks (Fig. 100), either proceed in company 

 with the bloodvessels, thus forming the deep lymphatics, or else run 

 on the surface of organs, or in the subcutaneous cellular tissue of 

 the body and limbs, so forming the superficial lymphatics. From all 

 parts of the body, they run towards the root of the neck, where they 

 end in the venous system. More numerous than the bloodvessels, 

 they pursue an irregular course, often unite and again divide, and 

 present, in certain situations, as especially seen in young subjects, 

 small retia mirabilia or lymphatic networks, inclosed in a thin areolar 

 investment. They, moreover, pass through the bodies known as lym- 

 phatic glands, which may be regarded as more highly and specially 

 developed retia (p. 60). Ultimately, the lymphatics of the lower 

 limbs, of the lower half of the trunk, of the left side of the head and 

 neck, and of the left upper limb, join 

 the great trunk of the lymphatic sys- 

 tem, the thoracic duct, a. Those from 

 the right side of the head and neck, 

 and right upper limb, unite to form a 

 small separate trunk, named the right 

 lymphatic duct. This enters the ve- 

 nous system at the point of junction 

 of the right jugular and subclavian 

 veins, its orifice being guarded by a 

 double valve. A few separate and 

 smaller lymphatic trunks are also said 

 to enter the veins of the neck at differ- 

 ent points. All the organs of the 

 thoracic and abdominal cavities, have 

 superficial as well as deep lymphatics 



belonging tO them, FigS. 100, 101. Fi S- 101. Superficial lymphatics upon the heart, 



The lymphatics were first described rituated beneath the MroM coat or visceral part 



, ^.y*. r . /i c /i\ T- iv J of the pericardium. The figure also serves to 



by Jballopms (1561), but afterwards ph ow the shape, position, aud subdivisions of the 



much more fully, by Rudbeck and heart. 1, the left, 2, the right auricle ; 3. the 



Bartholin; the thoracic duCt Was de- lefl > 4 ' the "S ht ventricle; 5, the descending 

 , , Ip, . . , ... - ,_,_ m part of the arch ot the aorta. 



tected by .bustacnms (obnt. Io70). 



The thoracic duct (Fig. 100 a], begins below by a dilatation, named 

 the receptaculum chyli, usually placed upon the second lumbar vertebra. 

 From this point, the duct ascends, somewhat tortuously, in front of 

 the vertebral column, into, and through, the thorax. Placed, at first, 



Fig. 101. 



