THE LYMPHATIC VESSELS OF THE SEROUS MEMBRANES. 45 



nitrate of silver, arid artificial respiration is carried on for fifteen to 

 twenty minutes, the animal being suspended head downwards. The 

 centrum tendineum, having been sufficiently washed witli water, is 

 cut out and prepared for microscopic preparations, as mentioned 

 above. In such preparations the lymphatics present themselves as 

 dilated sacs and tubes, the endothelial wall of which comes out with 

 great distinctness. Fig. 36 is taken from such a preparation. 



The fact that lymphatic vessels which have a winding course 

 sink down at once between the tendon-bundles, to continue their course 

 as straight vessels, is here very obvious. 



It can be further made out in such preparations that the horn-like 

 terminations of lymphatic capillaries, as represented by Reckling- 

 hausen, are only apparent, for they correspond to such points where a 

 lymphatic vessel curves round so as to sink down between tendon- 

 bundles and to become a straight vessel. In silver preparations 

 prepared in the ordinary way after pencilling, such horn-like termin- 

 ations are sometimes pretty common, and can easily be mistaken for 

 true terminations. 



The question presents itself now, What is the physiological value 

 of the straight lymphatic vessels? Ludwig and Schweigger-Seidel 

 already attributed to these straight lymphatics an important part in 

 the absorption. According to those authors they are widely dilated 

 during the inspiration position of the diaphragm, corresponding to 

 the action of the muscles and tendons of this latter, whereas they are 

 compressed during the respiration, the lymphatics of the pleural 

 surface of the diaphragm being quite the reverse. Consequently, the 

 respiratory movement of the diaphragm acts like a pump on its 

 lymphatics. (The free communication of the lymphatics with the 

 peritoneal cavity, by means of stomata, will be discussed hereafter.)' 

 This, however, is not the only way in which the straight lymphatics 

 act. We have mentioned before that the lymphatics of the diaphragm 

 are arranged in an anterior and posterior system, the former dis- 

 charging itself in trunks that run towards a gland, the latter in a wide 

 short trunk that runs directly into the thoracic duct. Now the 

 straight lymphatic capillaries are the vessels which perform the com- 

 munication of those two systems, and this is their chief action. As the 



