MILLER — CONTRIBUTIONS FROM ANATOMICAL LABORATORY. 239 



point evidence in support of their idea without viewing the sub- 

 ject in an impartial manner. 



The frog seems to have been especially studied, although the 

 toad, rabbit and Guinea-pig have frequently been used. The 

 membranes which have been most studied and where stomata 

 have been most frequently described are the diaphragm of the 

 rabbit and the mesentery of the frog. In a few instances the 

 cat, mouse, dog, and in one case man, has been made the subject 

 of investigation. The central tendon of the diaphragm has also 

 been an object of special study, but the investigators fail to 

 agree; the same may be said of studies of other serous mem- 

 branes. Yet in spite of these facts we are told "that stomata 

 are found with certainty in the serous membranes of all small 

 animals" (Krause). 



The methods of investigation may be classified as follows, viz., 

 1, absorption ; 2, injection ; 3, impregnation. 



Absorption. This method depends upon the penetration of 

 solutions into the superficial lymphatics and was formerly much 

 used. Milk, blood, etc., were placed in contact with the cen- 

 tral tendon of the diaphragm and after a little most of the fluid 

 would be absorbed. Colored fluids, such as a solution of Berlin 

 blue, or fluids holding fine granules in suspension, as carmine or 

 Chinese ink, have been used. They were either introduced into 

 the body cavity or merely brought in contact with the diaphragm 

 by allowing them to drop on its peritoneal surface. Artificial 

 respiration has also been used to promote absorption ; it being 

 claimed that it had a direct influence — acting as a pump (Lud- 



wig). 



Injection. This may be done either by the "puncture 

 method" or by inserting a fine canula directly into a lymph- 

 vessel. Dybkowsky (4) claimed that by injecting the lymphat- 

 ics it could be shown that the superficial lymphatics of the 

 intercostal pleura lead freely between the endothelium of the 

 surface by short vertical branches. Schweigger-Seidel and 

 Dogiel (21) conclude from an injection of the cy sterna lym- 

 phatica magna of the frog that the body cavity was in open com- 



