54 THE FROG CHAP.III 



cleaned, and one which has been kept from the first in 

 spirit or formaline : the latter is the more instructive (see 

 also the paraffin method, p. 473). An additional skull should 

 be carefully cleaned, and then boiled until the numerous 

 bones become separated from one another or disarticulated. 



After observing the form and relations of different parts of 

 the skeleton as described on pp. 35 and 36 (Fig. 8, A), they 

 may be separated from one another for more detailed 

 examination. The individual vertebrae should be strung 

 on a piece of wire or string so as to prevent them from being 

 lost or misplaced. 



With the specimen before you, work through the 

 characters of the axial skeleton (pp. 36-46) : if you omit 

 the details given in small type at the present stage, do not 

 forget to examine them subsequently. Make sketches of 

 a. any one of the vertebrae from the ist to the yth, from the 

 side and from the front or back ; b. the ist vertebra ; c. the 

 urostyle ; d. the skull from above and from below ; and 

 e. the hyoid. 



It requires considerable skill to make a satisfactory 

 preparation of the chondrocranium, and it is advisable to 

 examine that of a Dogfish first ; but if you wish to attempt 

 it, procure a large skull which has not been dried, and boil 

 it in water. Carefully separate, by means of a scalpel, most 

 of the investing bones (p. 43) ; the palatines, pterygoids and 

 quadratojugals, and the dentaries and angulosplenials 

 cannot well be disarticulated without destroying the soft 

 cartilaginous parts beneath them. 



Make out i. The brain-case and its fontanelle sand nerve- 

 apertures. 2. The olfactory capsules. "3. The auditory cap- 

 sules. 4. The palatoquadrate bar (to which the palatine, 

 pterygoid, and quadratojugal bones have been left attached). 

 5. The mandibula,' or Meckel's cartilage (to which the 

 angulosplenial and dentary have been left attached) . 6. The 

 replacing-bones (exoccipitals, pro-otics, sphenethmoid, and 

 mento-meckelians). 7. The columella, stapes, and fenestra 

 ovalis. 



Sketch from above and from below. 



Now proceed to examine the appendicular skeleton 

 (pp. 46-52), and sketch the shoulder-girdle and fore-limb, 

 and the hip-girdle and hind-limb. 



Split some of the longer limb-bones longitudinally with 

 a knife, and note the marrow-cavity in the shaft (Fig. 13). 

 Place another of the long bones in 10 per cent, hydrochloric 

 acid for an hour or two ; wash thoroughly in water and 

 examine. 



