56 



In most cases, however, beyond the heart and 

 large vessels leaving it, very little is investigated. Now 

 in the whelk it is quite easy to demonstrate all the more 

 important facts in connection with the circulation, and if 

 a little care is used in injecting, there is no reason why 

 this method should not be adopted in the ordinary 

 laboratory classes for senior students. Very few complete 

 accounts have been given of prosobranch blood systems, 

 and it is hoped that this description will serve as an aid 

 in the study of an excellent and exceedingly common 

 type. 



A great part of both the venous and arterial systems 

 can be made out from the surface, without any dissection. 

 All the vessels shown in figure 35 on Plate V can be seen, 

 with the exception of the dotted trunks which run in the 

 foot. This means that a cold injection mass may be used, 

 without troubling to employ any of the complicated and 

 unsuccessful mixtures which have been invented in order 

 to attain solidification or coagulation in the vessels. 



Directions for Injection. 

 For students' purposes, two very simple injecting 

 masses will suffice: — 



1. — Cold Injecting Mass. — Use one of the familiar 

 collapsible tubes of artists' oil colours. Chrome-yellow is 

 a convenient tint. Squeeze this into a dish and dilute with 

 turpentine, stirring until a slightly thick but uniform 

 mixture is produced. 



2. — Hot Injecting Mass, for studying the deeper 

 vessels. — Melt down one or two pieces of ordinary table 

 jelly in an evaporating dish, adding water if necessary. 

 Add to this some carmine, rubbed down with a small 

 quantity of water in a mortar and stir until a uniform 

 mixture is obtained which will solidify on cooling. 



