CHAP. XXVI.] STRUCTUKE OP THE ABSORBENTS. 



273 



Fig. 169. 



A. Longitudinal wavy fibres on the inner surface of the 

 contractile transverse fibres of the thoracic duct of the 

 horse. Magnified 80 diameters. 



B - Stratum of nucleated epithelial cells lining the lym- 

 phatic vessels ._ From alarg *; i ymp hatic on the trachea of 

 a horse . Magnified 320 diameters. 



Fig. 170 



A 



of a single layer of extremely delicate nucleated particles, first no- 

 ticed by Henle. They are 

 usually spindle-shaped, and 

 fitted side-ways to each 

 other (fig. 169 B). 



The valves (fig. 170 C) are 

 formed by a process of 

 fibrous membrane standing 

 off into the vessel, probably 

 with a covering of the epi- 

 thelium. They are mostly 

 in pairs, of a crescentic 

 shape, the convex edge at- 

 tached, the concave free, 

 and when in action consti- 

 tute a perfect barrier, the 

 wall of the vessels immedi- 

 ately above them being 

 bulged into a sinus, so as to 

 give the canal a beaded ap- 

 pearance when distended. 

 Mr. Lane has observed that 

 some of the valves are single 

 and circular, with a central 

 perforation, and therefore 

 incomplete while others 

 are unequal in size. 



Contractility of the Absorb- 

 ent Vessels. This depends 

 on the contractile tissue of 

 their proper coat. The pro- 

 perty may be demonstrated 

 by mechanically irritating 

 a large vessel, such as the 

 thoracic duct, in an animal 

 just killed it undergoes 

 slow contraction. The ab- 

 sorbent Vessels Continue to A. One of the inguinal lymphatic glands injected with 

 -, , -, . mercury, a. Afferent lymphatic vessel from the lower 



propel their Contents, even extremity. ft. Efferent vessel. Others are also seen. 



-. .-, , p ,i B. One of the superficial lymphatic trunks of the thigh. 



When me Current trom tile c. One of the femoral lymphatic trunks, laid open longi- 

 i T tudinally to display the valves within it. c. Sinus between 



primary netWOrKS IS arrested the valve and the wall of the vessel, d. Surface of one 

 -i . i , i valve, directed towards the opposite, e. Semicircular at- 



by pressure, and thlS they tachecl margin of the valves. After Mascagni. 



