18 T. CHARTERS WHITE ON THE INJECTION OP 



the ribs on each side of the chest ; never mind the intercostal 

 vessels, they will not let out much injection, at any rate nothing to 

 signify. 



Now, although life may be perfectly extinct, the muscular con- 

 tractility of the heart will exert itself, and the pulsation of that is 

 an indication of the elasticity of the vessels ; when once that has 

 ceased the injection will not flow so freely, as an impending rigor 

 mortis will have taken possession of the coats of the vessels, and 

 will be a serious hindrance to the access of the fluid into the capil- 

 laries ; lay open the pericardium, the bag which envelopes the 

 heart, and you will see the aorta springing from the left ventricle, 

 and arching over by the left side of the spine, descending to the 

 abdomen; cut off the apex of the heart, and insert the nozzle you 

 have prepared, first taking the precaution to fill it and the attached 

 tube with water; push it gently upward through the cavity of the 

 heart till you see it enter the aorta, when with a curved needle you 

 may pass a ligature under aorta and pipe, and tie them, securely 

 fastening the ends of your ligature to the wire studs twisted on 

 your glass tube ; that will prevent it slipping out again; see that it 

 is filled with fluid to the top, so that all air may be excluded, and 

 then make your connection with the stop-cock, first letting a few 

 drops of the injection flow through it ; when your tube is continuous 

 turn on the stop-cock, and you will soon see the various organs 

 become tinged with blue, the larger vessels first, and coursing 

 along these, it will branch off into innumerable fine channels, till 

 the whole capillary system is full ; and the excess coming out of 

 the right side of the heart will tell you your work is complete. 



Your subject may remain to be cut up at your leisure, for the 

 glycerine in the injection will act as a preservative for some con- 

 siderable time. This, then, was the process adopted for the in- 

 jected preparation under my microscope this evening. You 

 will see that the blue fluid has run into the finest capillaries. But 

 it is said we learn more from our failures than from our successes ; 

 and therefore, as that preparation is far from what you can admire 

 from an aesthetic point of view, it will prove all the more instructive 

 if I point out an error I fell into. You will see that in a great 

 many places the blue injection has entirely faded out, and in others 

 that it is very pale. I believe this has arisen from the blue fluid 

 not being sufficiently acid to neutralise the alkalinity of the blood 

 remaining in the vessels ; and this seems substantiated by those 

 specimens where the preparation has been put into ammoniacal 



