ii PRACTICAL DIRECTIONS 33 



Having thus exposed the whole of the abdominal cavity, 

 pour just enough water into the dissecting-dish to cover the 

 animal, first washing away any blood which may have es- 

 caped from cut vessels. If your specimen is female, dissolve 

 a little common salt in the proportion of i per cent, in the 

 water (i gramme to 100 c.c.), or mix it with about one-third 

 of its bulk of methylated spirit, in order to prevent the 

 excessive swelling of the oviducts. (If, however, you wish 

 to make out the blood-vessels in this specimen without 

 injecting them, it is as well to defer putting water into the 

 dish until a later stage of dissection.) 



Note 



1. The peritoneum parietal and visceral layers. 



2. The pericardium, containing the heart. If not already 

 opened, the pericardium should be slit through, so that the 

 auricles and ventricle can be plainly seen. If the frog has 

 been killed quite recently, you will be able to observe the 

 pulsation of the*heart. 



3. The right and left lobes of the liver, and the gall- 

 bladder. 



4. The two lungs : if contracted, inflate with a blowpipe 

 through the glottis. 



5. The enteric or alimentary canal, consisting of gullet or 

 oesophagus, stomach, small intestine (duodenum and ileum), 

 and large intestine or rectum communicating with the cloaca, 

 which will be seen at a later stage, and which opens to the 

 exterior by the vent. 



6. The mesentery. 



7. The pancreas. 



8. The spleen. 



9. The urinary bladder. If collapsed, insert a blowpipe 

 into the vent and inflate. (You will very likely find some 

 small parasitic flat-worms, called Polystomum integerrinum, 

 in the bladder ; each worm has a ring of suckers round the 

 hinder end.) 



10. In the male the spermaries and fat-bodies, and in the 

 female the ovaries, fat-bodies and oviducts. 



11. The kidneys and ureters. 



12. The mode of suspension of all these organs (p. 26), 

 and the position of the sub-vertebral lymph-sinus. In order 

 to understand clearly the relations of these parts, a thick 

 transverse section should be made through another frog in 



PRACT. ZOOL. -n 



