INJECTION INTO THE CIRCULATION. 189 



This, however, is fallacious. This vessel lies very loosely 

 imbedded in connective tissue, and in eiforts to intro- 

 duce a needle into it, rolls about to such an extent that 

 only after a great deal of difficulty does the experiment 

 succeed. On the other hand the posterior branch 

 (ramus latefalis posterior of the vena auricularis poste- 

 rior) is a very fine, delicate vessel which runs along the 

 posterior margin of the ear, and which is so firmly fixed 

 in the dense tissues which surround it that it is pre- 

 vented from rolling about under the point of the needle. 

 The further away from the mouth of the vessel — that 

 is, the nearer we approach its capillary extremity — 

 the more favorable become the conditions for the success 

 of the operation. 



Select, then, the very delicate vessel lying quite close 

 to the posterior margin of the ear, and make the injec- 

 tion as near to the apex of the ear as possible. The 

 injection is always to be made from the dorsal surface 

 of the ear. 



Of no less importance than the selection of the proper 

 vessel, is the shape of the point of the needle employed. 



The hypodermatic needles as they come from the 

 makers are not suited at all for this operation because 

 of the way in which their points are ground. If one 

 examines carefully the point of a new hypodermatic 

 needle it will be seen that the long point, instead of 

 presenting a flat, slanting surface, when viewed from 

 the side, is more or less of a curved surface. Now, in 

 efforts to introduce such a needle into a vessel of very 

 small calibre, it is commonly seen that the extreme 

 point of the needle, instead of remaining in the vessel, 

 as it would do were it straight, very commonly projects 

 into the opposite wall, and as the needle is inserted 



9* 



