THE COD. Ill 



of about 90 per cent. If a second specimen is to be 



dissected, the examination of the external features 



of the brain may be postponed, and the organ 



placed in alcohol at once. 



XXII. Place the fish once more on its right side, and 



by turning forward the lobes of the liver, and, 



when necessary, dissecting away the peritoneum 



from the viscera, blood-vessels, &c., make out the 



following: — ' 



119. The divisions of the alimentary canal (Fig. 31): the 



oesophagus passes insensibly into the stomach, the cardia 



or aperture of communication between the two being marked 



only by a difference of colour and texture ; the stomach 



passes back to the hinder end of the abdomen, becomes 



bent upon itself towards the right side, and narrowing, 



becomes continuous with the small intestine, the pylorus 



or aperture of communication between the two being marked 



by the attachment of the pyloric cjeca {fy.c) ; the first loop 



of the intestine is U-shaped and represents the duodenum 



{dm); this is followed by the ileum (//), which after a 



^ The injection of the blood-vessels, which is necessary for their 

 satisfactory examination, is best performed in the following way : (a) 

 Make a small incision into the bulbus arteriosus, and insert a cannula 

 directed forwards ; from this the ventral aorta and afferent branchial 

 arteries are injected : {l>) insert a second cannula into one of the branches 

 of the mesenteric artery, e.g. that supplying the pyloric ca;ca, directing 

 it forwards, or towards the proximal end of the artery; from this the 

 dorsil aorta and efferent branchial arteries are filled . {c) a third can- 

 nula is inserted into one of the factors of the portal vein, e.g. that 

 comin" from the pyloric caeca, its point being directed forwards or 

 towards the main portal vein, which is in this way thoroughly injected : 

 (d) a fourth cannula is inserted, pointing forwards, into the spermatic 

 vein (§ 126) ; from this the main sys'emic veins are easily filled. Plaster 

 of Paris, or some other cold injecting material, must be used ; as a very 

 slight heat causes gelatinization of the connective tissue of the blood- 

 vessels and their consequent rupture. 



