DISSECTION OF THE VISCERAL CAVITY. 35 



{hallux), has two phalanges j the second, third, and fourth 

 toes three each, the terminal bone on each being long 

 and claw-like. The fifth digit has, according to the 

 homology accepted for the bone on the fibular side of 

 the distal row of the tarsus, either three or two pha- 

 langes ; the terminal one, in correspondence with the 

 absence of a claw on it (5, c), is rudimentary. 



77. General Dissection of the Plenro-peritoneal Cavity. 

 Kill a terrapin with chloroform in the manner above 

 described (2); saw through the bony bridges uniting 

 carapace and plastron, and, with scissors, divide the skin 

 in front and behind, close to the plastron, and then 

 placing the animal on its dorsum, gradually raise the 

 plastron from before back. Dissect away, with a scalpel, 

 the soft parts attached to its inner surface ; cut close 

 to the bone, so as to avoid, as far as possible, all injury 

 to the soft parts. As you separate the plastron, note 

 the stout ligaments passing to it from the precoracoids. 

 When the plastron is removed note the fibrous perios- 

 teum covering it on its dorsal side, and the attachments 

 of muscles to it. 



78. On the ventral aspect of the animal, as exposed 

 by removing the plastron, observe : 



a. The semi-transparent pericardium, and, seen 

 through it, the heart, which may still be beat- 

 ing. 



b. Anteriorly, the muscles on the pectoral arch, 

 and the bones of the latter which can be felt 

 through them ; posteriorly, the pelvic arch, 

 which can be likewise felt through the muscles 

 over it. 



