57 



It is absolutely essential that the whelks to be 

 injected be dead, and further that they have died in a 

 thoroughly lax uncontracted state. The best means is to 

 allow the whelks to expand in a small quantity of sea-water 

 and then add carefully a few drops of a 2 per cent, solution 

 of cocaine in 90 per cent, spirit; and continue adding 

 gradually a little of the cocaine solution. It will be 

 found that three days are necessary before the animals 

 become irresponsive to stimuli. By that time the water is 

 probably in very bad condition, but the whelks will not 

 be seriously affected by this, so far as injection is con- 

 cerned. Tne shell should now be removed piece by piece 

 with a pair of bone forceps, and great care must be taken 

 that the soft tissues are not damaged. The columellar 

 muscle should be detached from the shell with a scalpel. 



On the external surface the position of the mucous 

 gland and the gill should be made out. Those two organs 

 of the pallial complex with the osphradium can be seen 

 through the mantle. The pericardium has been already 

 seen, lying at the side, and under, the kidney. 



Injections can be made from three places. 



1. — The syringe should be inserted into the efferent 

 branchial artery, with the point towards the heart. This 

 vessel can be seen quite easily, forming the ventral 

 boundary of the gill. If the paint mixture is used, a very 

 clear view will be obtained of the branchial vessels, the 

 vessels of the mucous gland, and the reno-mucous vessel 

 (fig. 35, Mu. gl., Br. v., R. sin.). The auricle will be 

 filled, and probably the efferent renal vessels (fig. 35, 

 Ren. eff.). 



2. — The point of the syringe should be plunged into 

 the foot, so that it reaches somewhere in the space in 

 which the alimentary canal and poison gland lie. This 

 injection will fill the extensive venous sinus, and then 



