234 THE MICROSCOPE. 



injecting pipe is to be inserted. Where the vessels are 

 large, a needle commonly known as an aneurism needle 

 answers the purpose very well. The thickness of thread 

 must vary according to the size of the vessel. The silk 

 used by surgeons will be found the best adapted for the 

 purpose, and not too thin, or it may cut through the 

 vessel. 



When the size and the subject have both been properly 

 prepared, have the injection as hot as the fingers can well 

 bear. One of the pipes g, fig. 141, must then be placed in 

 the largest artery of the part, and made secure by tying. 

 Put the stop-cock / into the open end of the pipe e, and 

 it is then ready to receive the injection from successive 

 applications to the syringe a, leaving sufiicient space only 

 for the piston c. The injection should be thrown in by a 

 very steady and gentle pressure on the end of the piston- 

 rod. The resistance of the vessels, when nearly full, is often 

 considerable; but it must not be overcome by violent 

 pressure with the syringe. When as much injection is 

 passed as may be thought advisable, the preparation may 

 be left (with the stop-cock closed in the pipe) for twenty- 

 four hours, when more material may be thrown in. 



As the method of injecting the minute capillaries with 

 coloured size is often attended with doubtful success, 

 various other plans have been proposed. Ruysch's method, 

 according to Rigerius, was to employ melted tallow coloured 

 with vermilion, to which in the summer a little white wax 

 was added. Monro recommended coloured oil of turpen- 

 tine for the small vessels ; after the use of which, he threw 

 in the common coarse injection. This is made of tallow 

 and red lead, well mixed and heated before it is used. 

 The cold paint injection succeeds well if thrown carefully 

 into the minute arteries; but its tendency to become 

 brown by age is an objection to its use. 



Professor Breschet frequently employed with success milk, 

 isinglass, the alcoholic solution of gum-lac, spirit varnish, 

 and spirit of turpentine ; but he highly recommends the 

 colouring matter extracted from Campeachy, Fernambone, 

 or Sandal woods. He says : " The colouring matter of 

 Campeachy wood easily dissolves in water and in alcohol : 

 it is so penetrating that it becomes rapidly spread through 



