52 ZOOTOMY. 



in the male (Fig. \?>, pn.d, see §§ 117 and 118.) The 

 former are attached to the dorsal (under, in the present 

 position,) surfaces of the shoulder girdle by a distinct 

 ligament. 



XXI. Remove the liver, taking care not to injure 

 the hepatic sinus or oviducts : cut through the 

 stomach Just beyond its junction with the oeso- 

 phagus : cut through the rectum just anteriorly to 

 the rectal gland : remove the alimentary canal 

 between these two points. 



Wash out the contents of the alimentary canal by dh-ecting a stream 

 of water through it, then fill with a o'5 per cent, solution of chromic 

 acid, by tying one end, pouring in the acid through a small funnel or 

 injecting it with a syringe, and when full, tying the other extremity : 

 place in a vessel of the same solution for a few days : \vhen sufficiently 

 hardened, cut windows in various parts and make out 



105. The pyloric valve, a fold of mucous membrane extending 

 between the stomach and intestine, and opening to\: ards the latter. 



106. The spiral valve, commencing in the duodenum as a simple 

 inwardly-directed fold of the mucous membrane, and in the colon 

 becoming a spiral inclined plane which finally terminates at the com- 

 mencement of the rectum. The development of the spiral valve varies 

 almost indefinitely : its width may be either less than, equal to, or 

 greater than the semi-diameter of the gut : the plane of any part of it 

 may be either at right angles to the long axis of the intestine, or in- 

 clined to it in either direction. There is also much variation in the 

 number of turns of the spiral and in the character of the mucous 

 membrane. 



107. The irregularly longitudinal ridges or rugse of the stomach. 



108. The network of fine ridges, covering the interior of the intestine 

 and the spiral valve. 



XXII. If the fish is not injected, make a small aperture in the 

 sinus venosus, introduce u blowpipe directed outwards, and 

 inflate. 



109. If nothing has been cut, a large inflated sac will be seen in the 

 middle of the abdominal cavity, between the genital glands : this is the 

 great cardinal sinus (Fig. 17, cd.s), formed by the union in the 

 middle line of the two posterior cardinal veins [cd], by which the blood 



