220 



THE FROG— THE PLATANA 



3. Make a preparation and a sketch of the huid-limb showing the femur, 

 tibio-fibula, astragalus, calcaneum or os calcis, and the other bones of the tarsal 

 region, five meta-tarsals, and digits. Number the digits from the inner side. 



JUdio-utna 



Fig. 78.,— The Hind-limb and the Fore-limb of Xenopus. 

 B. The Vertebral Column. 



1. Remove the skin and muscles from the dorsal surface of the back to show 

 the nine vertebrae and the urostyle. Make a drawing showing the vertebrae 

 with their transverse processes, and the urostyle attached to the posterior end 

 of the 9th vertebra. 



The 2nd to the 9th vertebrae bear long transverse processes produced 

 outwards. The urostyle is attached to the 9th vertebra by two facets. 



[In the Platana the 2nd, 3rd, and 4th vertebrce bear long transverse processes 

 curved backwards, those of the 3rd arid 4th being tipped with small cartilaginous 

 ribs. The transverse processes of the 5th, 6th, 7th, and 8th vertebrce are sletider and 

 project forwards and outwards. The 9th vertebra has long wing-like processes, attached 

 to which are the ilia of the pelvic girdle. The urostyle is fused, to the 9th vertebra.] 



Note the intervertebral discs and the intervertebral foramina for the exit of 

 the nerves from the spinal cord. 



2. Remove, examine, and draw the 1st or atlas vertebra, noting its ring- 

 like form, the absence of transverse processes, and the concave facets by which 

 it articulates with the two occipital condyles of the skull. 



3. Remove, examine, and draw the 3rd vertebra, noting the procoelous ^ 

 centrum, neural arch and neural spine, anterior and posterior zygapophyses, 

 and the transverse processes. 



[The centrum is opisthoccelous ^ in the Platana, and each transverse process 

 bears a cartilaginous rib.] 



1 Proocelous means concave in front and convex behind. 



2 Opisthoccelous means convex in front and concave behind. 



