14 



E. The Skeleton. 



Before beginning the examination of the skeleton the frog may be immersed for 

 two or three minutes in boiling water. 

 1. The skuU. 



a. Eemove the skin and subcutaneous tissues from the roof of the skull, 



and observe the parieto-frontals and nasals, the premaxillse, maxillae, 

 and squamosals, the quadrato-jugals, and the exposed portions of the 

 exoccipitals, prootics, and sphenethmoid. 



b. Eemove the mucous membrane from the roof of the mouth, and 



observe the parasphenoid and vomers, the pterygoids, and palatines, 

 and the under surface of the maxillae, premaxillsB, and quadrato- 

 jugals, and the exposed portions of the exoccipitals, prootics, and 

 sphenethmoid. 



c. Examine the mandibular arch — 



(a) The upper portion (quadrate cartilage) known as the suspen- 

 sorium ; note that it supports the squamosal, and serves by its 

 lower end for the attachment of the mandible, while it is united 

 by its upper end to the auditory capsule. 



(6) The lower portion or mandible, each half of which consists partly 

 of cartilage (Meckels), and partly of cartilage bones — the long 

 angulo-splenial underneath, and the small mento-meckelian at 

 the symphysis, and the dentary on the upper margin. 



d. Examine the hyoid arch, noting — 



(«) The columella in connection externally through a piece of cartilage 

 (suprastapedial) with the membrana tympani, and fixed by its 

 inner end to the stapes. 



(&) The anterior process of the hyoid attached to the auditory capsule 

 below the fenestra ovalis. 



(c) The body consisting of the fused ventral portions of the hyoid and 

 the four branchial arches of the tadpole. 



(d) The ossified posterior processes (remains of fourth branchial 

 arch) which project obliquely backwards one at each side of the 

 larynx. 



e. Draw (2 nat. size) — * 



(a) The hyoid arch, showing the anterior and posterior cornua, and 

 the short processes from the angles of the body. 



(b) The upper surface of the skull, showing — 



(1 ) The membrane bones, — parieto-frontals, nasals, premaxillae, 



maxillae, and squamosals. 



(2) The cartilage bones, —exoccipitals, sphenethmoid, prootics, 



and quadrato-jugals. 



(c) The under surface of the skull, showing — 



(1) The membrane bones, — parasphenoid, vomers, premaxillse, 



and maxillae. 



(2) The cartilage bones, — exoccipitals, sphenethmoid, pterygoid, 



palatine, prootic, and quadrato-jugals. 



(d) The mandible, showing Meckels, cartilage, and the angulo-splenial, 

 mento-meckelian, and dentary bones. 



* The cartilage should be coloured blue, and the cartilage bones doited by way of 

 diatinguishing them from the membrane bones. 



