THE COD. 87 



by carefully dissecting away the muscles, &c., 

 while fresh, without either boiling or maceration, 

 the bones being kept together in their natural 

 position by their ligaments. Of this skull it is as 

 well to make a longitudinal vertical section by 

 sawing through the brain-case a little to one side 

 of the middle line and cutting through the mandi- 

 bular and hyoidean symphyses (51 and 52) : from 

 the worst side, the jaw apparatus should be removed 

 from the brain-case by disarticulating the palatine 

 ( 46, Fig. 29, pa) and the hyomandibular ( 40, 

 Fig. 29, km). In the first skull the bones of the 

 brain-case may be separated from one another by 

 boiling for a considerable time and then gently 

 pulling them asunder. 



It is advisable to examine the second or entire skull 

 before drying, so as to see its cartilaginous, 

 portions ( 47, 49, &C.). 1 



II. In the skeleton as a whole note the following 



regions : 



i. The vertebral column, consisting of (a) trunk 

 vertebrae, bearing movable ribs which do not unite 



1 Owing to the small amount of cartilage left in the adult cod's skull, 

 the beginner will find some difficulty in seeing the relation between it 

 and that of the skate. A useful intermediate type is furnished by the 

 salmon or trout, in which there is a cartilaginous brain-case, quite 

 readily comparable with that of the skate but containing the occipital 

 and otic bones, basi- and pre-sphenoid, as endogenous ossifications : the 

 remaining homologues of the bones of the cod's brain-case (parietal^ 

 f rentals, parasphenoid, vomer, &c.) are seen to be membrane-bones, 

 easily detachable without injury to the cartilage (see Parker and 

 Bettany, Morphology of the Skull, p. 66). The skull of the salmon 

 or trout should be prepared like that of the cod, by b iling ; the brain- 

 case, Meckel's cartilages, &c., may be preserved by the glycerine jelly 

 process, described on p. 2. 



