PLATE IV. 



FlG. 17. Injection syringe, one-third of the actual size. 



FH;. n.-Suppoit for the study of the circulation in the web of the frog. It must be so arranged that the large 

 hole is just opposite the stage aperture of the microscope. (.S-c description in text, p. 4J.) It may also lie used fur 

 the study of the tongue. For this purpose half of a ring of cork must be fixed with brass plus round the hole on 

 the side next the end of the board. To this cork the comua of the tongue may be attached. 



FIG. 20. a & b. Injection cannulas, actual sizes. 



FIG. 21. Section knife. In the left-hand comer transverse section of the blade. 



FIO. i3.-Nozzle of injection syringe, at 



FIG. 19. Support for studying the circulation in the mesentery of the frog. a. Board on which the frog lies. 

 c. Glass disk on which the mesentery rests. 6. Trough for the reception of the coil of intestine, d. Object-glass 

 covered with cork. (Ill the text, p. 108, b and c are transposed.] 



