ON MINUTE INJECTIONS. 167 



how much pressure is necessary to fill but a single set of vessels. 

 After injection, a considerable time must be allowed for dry- 

 ing. Thin slices may then be cut off, and mounted either in 

 balsam or fluid. 



The villi of the intestines are beautifully exhibited after in- 

 jection. They should be macerated a little while in water, or 

 washed with a syringe, to remove the epithelium and mucus. 

 Animals that feed chiefly on vegetables have longer villi than 

 others. 



The lungs may be injected by the pulmonary artery or vein- 

 In a foetus, however, all the organs may be injected from the 

 umbilical vein. The author's injections and specimens of in- 

 jected lungs confirm the view of Mr. Rainey, that the essen- 

 tial and only true organs of the aeration of the blood are the 

 pulmonary capillaries. 



Injections of the skin may be made by the vein of an ex- 

 tremity. They may then be mounted in fluid, or after drying, 

 sections may be made and put up in balsam. 



The vessels of the choroid membrane and ciliary processes of 

 the eye are often injected in a foetus ; or in the case of an animal, 

 as a cat, rabbit, &c., injected from the heart. The preparation 

 should be kept in fluid. 



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

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

 ramifications of the small vessels. They should be very care- 

 fully handled, or moved, in the macerating liquor, as the slight- 

 est 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 usually injected with quicksilver, but 

 M. Rusconi and Professor Breschet, have abandoned this me- 

 thod for the colored material, on account of the mercury fre- 



