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HANDBOOK OF PHYSIOLOGY. 



ance; and the lympli in the lacteals during the period of digestion is 

 called chyle. There is no essential distinction, however, between lacteals 

 and lymphatics. In some parts of its course the lymph-stream must 

 pass through lymphatic glands. 



Lymphatic vessels are distributed in nearly all 

 parts of the body. Their existence, however, has 

 not yet been determined in the placenta, the um- 

 bilical cord, the membranes of the ovum, or in 

 'any of the so-called non-vascular parts, as the 

 nails, cuticle, hair, and the like. 



Origin of Lymph Capillaries. The lymphatic 

 capillaries commence most commonly either (a) 

 in closely meshed networks, or (b) in irregular 

 lacunar spaces between the various structures of 

 which the different organs are composed. Such 

 irregular spaces, forming what is now termed 



Fig. 279. Fig. 280. 



Fig. 279 Superficial lymphatics of the forearm and palm of the hand, ^.5. Two small glands 

 at the bend of the arm. 6. Radial lymphatic vessels. 7. Ulnar lymphatic vessels. 8, 8. Palmar 

 arch of lymphatics. 9, 9'. Outer and inner sets of vessels, b. Cephalic vein. d. Radial vein. 

 e Median vein. /. Ulnar vein. The lymphatics are represented as lying on the deep fascia. 

 (MascagnO 



Fig. 280. Lymphatics of central tendon of rabbit's diaphragm, stained with silver nitrate. The 

 ground substance has been shaded diagrammatically to bnng out the lymphatics clearly. I. Lym- 

 phatics lined by long narrow endothelial cells, and showing v. valves at frequent intervals. (Scho- 

 field.D 



the lymph-canalicular system, have been shown to exist in many tis- 

 sues. In serous membranes such as the omentum and mesentery they 

 occur as a connected system of very irregular branched spaces partly 

 occupied by connective tissue-corpuscles, and both in these and in many 

 other tissues are found to communicate freely with regular lymphatic 



