170 MANUAL OF HISTOLOGY. 



Recklinghausen' s observation, that communication exists be- 

 tween the abdominal and pleural cavities by means of small 

 openings in the central tendon of the diaphragm. By injecting 

 some insoluble coloring matter, held by fluid in suspension, 

 into the abdominal cavity, he obtained a fine injection of the 

 lymphatics of the central tendon, and was able to detect the 

 substance on its pleural surface. The experiment may be re- 

 versed by injecting the pleural cavity. He was able to see the 

 actual passage of milk-globules into these openings by remov- 

 ing a portion of the fresh tendon upon a cork ring, its pleural 

 surface upward, placing a drop of milk upon it, and observing 

 with the microscope the nearly round openings, large enough 

 to admit at once two or three of the milk-globules which ran 

 toward these openings in little eddies, and disappeared below. 

 He stained this membrane with nitrate of silver, and found 

 that the openings corresponded to perforations between the 

 endothelial cells leading perpendicularly or obliquely to the 

 lymphatics. Schweigger-Seidel and Doigiel observed similar 

 openings leading from the abdominal cavity, through the retro- 

 peritoneal membrane, into the cysternce lymphaticce magna of 

 the frog. Dybkowsky showed that colored fluids placed in the 

 pleural cavity were absorbed by the lymphatics of the inter- 

 costal pleura. Schweigger-Seidel, Doigiel, and Ludwig con- 

 firmed the observations of Recklinghausen in connection with 

 the central tendon of the diaphragm, and it is now generally 

 admitted that such openings exist, not always freely open, 

 however, but sometimes with a valve-like cleft. It must not 

 be understood that the small bead-like spots and the dark 

 spots between the cells are true stomata. It is not definitely 

 known, in fact, what they really represent. Oedmannson first 

 described them, not only on the serous membranes, but also 

 on the endothelial layer of the chyle- vessels. They are very 

 numerous directly over the lymph-vessels of the central tendon 

 on its peritoneal surface (Dybkowsky). 



Ranmer^s mews on false stomata. Ranvier has an in- 

 geneous theory explaining the formation of these objects, 

 which have been termed false stomata^ also of the true sto- 

 mata and the fenestra of the omen turn. He considers that the 

 lymphoid corpuscles, which are always to be found in serous 

 cavities, penetrate the membrane, making a depression or per- 

 foration, sometimes remaining, sometimes escaping again. In 



