THE FROG 



the microscope; the hole in the board will admit light re- 

 flected by the mirror. It may be more convenient to kill the 

 frog (by pithing) ; it may then be pinned to the board. In 

 such a preparation the circulation will usually continue for 

 several hours. 



The capillary circulation may also be demonstrated to 

 good advantage in the mesentery of a frog killed by pithing. 

 Cut through the body wall of one side of the abdomen and 

 pull out a loop of the small intestine. Pin this on a board 

 in such a manner as to spread out the mesentery and exhibit 

 in the same way as the web of the frog's foot. 



D. The Respiratory System. An entire specimen 

 should be prepared with the lungs exposed and inflated. If 

 blown up with air they may be hardened in that condition 

 in formalin. 



The vocal sacs of the male may be injected with gelatin 

 and exposed by removing the overlying integument. 



Permanent preparations of the hyoid apparatus, larynx 

 and lungs, dissected out as directed in the text, are required. 



Separate lungs partially inflated, then hardened in forma- 

 lin and cut open so as to expose the interior, should be ex- 

 hibited in small glass vials. 



E. The Skeleton.- -The following preparations are re- 

 quired, the number of each depending on the size of the 

 class : 



Complete articulated skeleton, with hyoid intact 

 Articulated skull. Disarticulated skull. 

 Cartilaginous cranium, in alcohol. 

 Pectoral girdle, in alcohol. Pelvic girdle. 

 Vertebral column, strung on wire. 

 Hand and foot, mounted on cardboard. 

 Hyoid apparatus, in alcohol. 

 Miscellaneous bones, disarticulated. 



