INJECTING. 121 



the first two bottles is filled and acts as a siphon and thus 

 conveys the water to the second bottle creating there a pres- 

 sure which in turn is communicated to the bottle, e, whic;h 

 contains the injecting material and which is thus forced out 

 into the subject. By elevating or depressing the bottle b any 

 desired pressure may be obtained. 



With the injecting apparatus a colored fluid is forced into 

 the vessels, rendering it very easy to trace them in dissecting. 

 In some cases a saturated solution of prussian blue is suffi- 

 cient for this purpose but it is better to employ albumen or 

 gelatine as a basis. 



Common gelatine is melted over a slow fire with the aid 

 of water, in the proportions necessary to make a stiff jelly 

 when cold. These proportions are usually given on the out- 

 side of the package. When melted, the coloring matter is 

 stirred in. This may be an aqueous solution of carmine or 

 Prussian blue. Vermilion and yellow ochre are sometimes 

 used but from their weight they are not readily held in 

 suspension. 



In injecting with gelatine the object must be first warmed 

 and then kept in warm water while the operation is being 

 performed, otherwise the jelly will set before the fine vessels 

 are filled. To ensure success the specimen injected should 

 be fresh, not alcoholic. When injected, the vessels should be 

 tied and the specimen put away to cool so that the jelly may 

 set. It is well to place it immediately in alcohol as that 

 reagent facilitates the process by the extraction of water. 



The place for the introduction of the injecting fluid varies 

 with the form operated upon, as well as the system to be 



