THE LYMPHATIC SYSTEM. 



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Lymphatic capillary net-works within connective-tissue layer of skin ; smaller 

 vessels belong to superficial net-work, larger to deeper. {Teichmann.*) 



rapid compensation for variations in the intraocular tension. From the anatomical 



standpoint, however, they are not to be regarded as actually parts of the lymphatic 



system, and the mention that they here receive is merely a tribute to their historical 



importance in the problem of the origin of the lymphatic capillaries. 



The Capillaries. — The lymphatic capillaries (Fig. 7S3), which are arranged 



in the form of net- works of very different degrees of fineness and complexity, closely 



resemble in structure the 



blood - capillaries, their Fig. 783. 



walls consisting of a 



single layer of endothelial 



plates, which, however, 



are usually larger and 



less regularly disposed 



than those lining the 



blood - channels. They 



differ from those of the 



blood - vascular system 



not only in their ultimate 



branches being closed, 



but also in their general 



appearance. Thus, they 



are of much greater 



calibre, their diameter 



varying from .030-. 060 



mm., while that of the 



blood-capillaries may be 



as little as .008 mm. ; 



they do not present the regularity of size and gradual increase or diminution of 



calibre noticeable in the blood-capillaries, but larger and smaller stems are indefinitely 



interspersed, and spindle-shaped or 

 Fig. 784. nodular enlargements may occur at 



irregular intervals throughout the 

 net-work. And, finally, as a result 

 of these peculiarities, the meshes of 

 the net-work are of very varying size 

 and form. 



The arrangement assumed by 

 a net-work depends largely upon 

 the tissue and organ in which it 

 occurs. In the integument, for in- 

 stance, the lymph-capillaries arrange 

 themselves in two more or less 

 distinct layers, a more superficial 

 one, composed of smaller capillaries, 

 and a deeper, coarser one, — numer- 

 ous communications necessarily 

 existing between the two. Both net- 

 works are confined to the dermis, 

 the more superficial one lying close 

 to its epidermal surface, while the 

 deeper one is situated in its deeper 

 layers, the distance between the two 

 varying according to the develop- 

 ment of the dermis in different 

 portions of the body and in different 



individuals. From the superficial layer loops or single capillaries project upward into 



the dermal papillae, and special portions of the net-work surround each hair-follicle and 



sudoriparous gland. 



* Das Saugadersystem. Leipzig. 1861. 



Blood- 

 vessel 





Lymph-cells 



Transverse section ot small lymph-vessel. X 210. 



