xiv THE LYMPH 517 



There are no lymph hearts in man and other mammals ; the 

 walls of the lymph vessels are, however, provided (as above stated) 

 with muscular elements, which interlace above the valves in 

 various directions (Fig. 238) in such a 

 manner as to suggest that they may, by 

 their rhythmical contraction, function as 



minute hearts (Foster). No direct observa- 



tions exist to confirm this theory. On the 

 other hand, there are certain data which ^ J 



indicate that some of the lymphatic vessels, 

 under given conditions, are capable of rhythm- 

 ical and peristaltic contractions and dilata- 

 tions in the direction of the current. Arnold V^r* 

 Heller observed under the microscope, in the 

 mesentery of a guinea-pig anaesthetised with 

 chloral hydrate, that the lymphatics succes- 

 sively contracted and relaxed (on an average 

 six times a minute) in the peristaltic direc- 

 tion from the periphery to the centre. This 

 observation is unsupported, and, generally 

 speaking, it must be held that the muscle cells 

 of the lymphatic walls behave passively, like 

 those of the blood-vessels, in regard to the A ! 

 normal lymph current. 



Pursuing the line of strict analogy be- 

 tween blood-vessels and lymphatics, it may 

 also be stated that the muscle cells of the ^ ! > 



lymphatics have an automatically oscillating 

 tonus, which may be modified or regulated 

 by the influence of special vascular nerves. ^ 



The recent work of Gley and Camus (1894- 

 1895) has made it possible, in the physiology 

 of the lymphatic vessels, to define accurately 

 certain fundamental ideas as to the dilator 

 and constrictor functions of the nerves which 

 influence the muscle cells of the receptaculum 

 chyli and the thoracic duct. After success- 

 fully overcoming some serious technical diffi- 

 culties, these two experimenters succeeded 

 in registering on dogs the pressure in the 

 receptaculum, when reduced to a closed 

 cavity, communicating below by a cannula 

 with a receiver filled with physiological saline, kept at low and 

 constant pressure ; above, it communicated by a second cannula 

 inserted into the thoracic duct with a small water manometer, 

 provided with a float and a lever writing on a smoked cylinder. 

 Fig. 247 gives a clear idea of the method. 



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