274 THE MICROSCOPICAL NEWS. 
Brain, kidney, and spinal cord, are rendered sufficiently hard for 
cutting into sections in three weeks: lung, liver, spleen, pancreas, the 
intestines, the tongue, etc., take a longer time, usually from five 
to eight weeks, A saturated aqueous solution of Picric Acid is 
sometimes used as a hardening agent; but its action as a very 
persistent yellow dye is much against its employment for this 
purpose. 
INJECTING SEPARATE PARTS. 
Having now described the method of injecting an entire animal, 
I shall pass on to an account of the modes of injecting different 
organs and parts of an animal. 
The Kidney. On account of the comparatively large size of the 
blood-vessels of the kidney, it is a very suitable organ for the 
beginner to practise upon. ‘The filling of the arteries should first 
be mastered, and afterwards the injecting of both the arteries and 
veins. To inject the arteries, tie the canula in the renal artery 
and throw in carmine mass or Prussian Blue. When the vessels 
are about half filled, the injection will begin to flow from the renal 
vein which should then be ligatured, and the vessels slowly filled. 
After this is done, place the organ in spirit or cold water to cause 
the jelly to set, and then cut it into pieces of a suitable size for 
hardening. A good preparation will show the medullary portion 
filled with long and slightly curved arteries running parallel to each 
other ; the artery or afferent vessel entering the Malpighian tuft, 
the vein or efferent vessel leaving it, and the whole of the vascular 
portion of the kidney surrounding the Malpighian tufts filled with 
a network of arteries, capillaries and veins. If a double injection 
is required, inject the vein first with Prussian Blue or Turnbull’s 
Blue, and afterwards the artery. The kidney of a rabbit is better 
than that of any other animal for making injected specimens. 
The Liver. If the entire animal has been injected from the 
aorta, only the vessels supplied by the hepatic artery will be filled. 
In this case, the portal vein should be injected with one colour, 
and the hepatic vein with another. 
The method of injecting the bile ducts in a satisfactory manner 
had long puzzled anatomists before Chrzonszczewsky introduced 
his method of natural injection. The animal having been chloro- 
formed, a solution of indigo-carmine is to be introduced into the 
jugular vein. The dose should be repeated several times, and the 
animal killed in about an hour and a half. The other vessels 
should then be filled and portions of the liver hardened and cut 
into sections as already described. 
The Spleen is injected either from the aorta, or from the splenic 
artery. 
The Pancreas should be injected from the aorta. This organ 
requires to be well hardened before being cut into sections. 
