28 ZOOTOMY. 



As some parts of the skeleton are more delicate 

 than others, it is advisable, after a very short 

 immersion in hot water, to dissect off as much of 

 the flesh as will readily come away, and then to 

 remove the branchial arches ( 40 and 41) and to 

 disarticulate the skull and pectoral fins from their 

 attachments to the vertebral column. The latter 

 can then, if necessary, be subjected to a second 

 immersion in hot water. In cleaning the skeleton 

 special care is required to avoid injury to the 

 branchial arches ( 41), the spiracular cartilage 

 ( 37), and the labial cartilages ( 34). 

 The skeleton must not be allowed to dry, but should 

 be either kept in spirit or prepared by the 

 glycerine jelly process described on p. 2, I. In 

 the latter case about three to five days' immersion 

 in the glycerine fluid, and two to three days in 

 glycerine jelly, is required. During the process of 

 drying, it will be found advisable to fix out any 

 parts which show a tendency to twist or warp 

 with pieces of wood or strappings of paper or 

 calico. 

 II. In the skeleton as a whole, note 



1. Its division into tf, vertebral column, including dorsal 

 and caudal fins ( 3 16) ; b, skull, composed of the brain- 

 case ( 17 33), and of a number of loosely-attached carti- 

 lages, consisting chiefly of the jaws and of the gill-arches 

 ( 34 4 1 ) ; c > shoulder-girdle and pectoral fins ( 42 49) ; 

 d, hip-girdle and pelvic fins ( 50 53). 



2. The superficial crust of ossification on nearly all parts 

 of the skeleton, except some of the smaller cartilages, 

 which are entirely uncalcified, and the centra of the 

 vertebrae, which are calcified in a special manner ( 5) : the 



