INJECTING SMALL VESSELS. 89 



some beautiful injections of the smallest capillaries are made ; but 

 sometimes it is a failure, owing to the too rapid evaporation of the 

 ether, and the clogging up of the vessels from the early deposition 

 of the solid colouring matter. Perhaps a solution of gum-mastic in 

 ether, coloured with fine vermilion, will answer the purpose better. 

 Prussian blue, mixed with an equal quantity of oxalic acid, Bnely pow- 

 dered and dissolved in water, which should be gradually added, and 

 afterwards the strong size solution, forms a very beautiful injection 

 for the capillaries of the lungs. 



A foetus may be injected by the umbilical vein ; the head, by the 

 carotids ; the liver, mucous membrane of the intestines, &c. by the 

 portal vein ; an extremity by the principal artery, ifec. 



In those cases in which we desire to examine the arrangement of 

 the different systems of vessels in the same tissue or animal, it becomes 

 necessary to use a distinct colouring matter for each system. M. Eobin 

 recommends blue for the arteries, yellow for the veins, red for the 

 portal veins, and white for the bile ducts, or renal tubes. 



Before portions of injected preparations are put up in the glass- 

 cells, they should be allowed to harden some time in the preservative 

 fluid they are intended to be kept in ; clean sections can then be 

 made with a sharp knife, and slightly washed in fresh fluid. ' If it is 

 intended to preserve them in Canada balsam, it will be found advan- 

 tageous to spread them out to dry, and wet the surface with a drop of 

 turpentine before they are finally immersed in the balsam ; a thin glass 

 cover must be pressed down on the injection. 



Many parts, after injection, require to be macerated in water, or 

 corroded by dilute muriatic acid, &c., in order to exhibit the ramifica- 

 tions of the small vessels. They should be very carefully handled, or 

 moved, in the macerating liquor, as the slightest force may break the 

 vessels. When corroded, the pulpy flesh is to be carefully washed away, 

 by placing it under a stream of water, flowing very slowly, or by the 

 use of a syringe with water. 



The lymphatics are now usually injected with coloured material 

 instead of quicksilver, as formerly. M. Rusconi employed a small 

 silver syringe, together with a. kind of trocar, of which the canula is 

 formed from the quill of the wing-feather of the quail or partridge, — 

 the trocar being a tolerably large-sized surgical needle, the point having 

 three facets. When desirous of injecting the lymphatic system of a 

 lizard, tortoise, &c., he says : " I seize with a small pair of forceps the 

 mesentery, close to the vertebral column, where the reservoir of the 

 chyle is situated, and I introduce into it the point of the trocar ; I 



