The blood of the bullock, sheep, and pig is very difficult to crystallise. By the method adopted by Gamgee of adding to defibrinated blood one-sixteenth its volume of ether, shaking until the mixture becomes transparent, and allowing to stand in an ordinary temperature for 48 hours, crystals may be obtained from the blood of the following animals:

1.Horse.
2.Bullock.
3.Sheep.
4.Pig.
5.Dog.
6.Cat.
7.Rabbit.
8.Squirrel.
9.Guinea-pig.
10.Rat.
11.Mouse.
12.Chicken.
13.Pigeon.

Crystals from human blood are not easily obtainable by this process, but when they are, they always give the spectrum of reduced hæmoglobin, whereas those from the animals mentioned above give the spectrum of oxyhæmoglobin.

Chemical Examination

Having obtained a coloured solution from a supposed blood-stain, if sufficient in quantity, apply the following chemical tests to separate portions:

1. Add a few drops of a weak solution of ammonia in distilled water. The colour may remain unchanged, or, at the most, a slight heightening may take place, if it be due to blood. If the solution of ammonia be too strong, a brown colour may be produced if blood be present.

2. Heat to boiling, when the following changes take place if blood be present:

(a) The colour may disappear.

(b) Coagulation follows.

(c) A precipitate falls, dirty grey or brown in colour, depending upon the amount of colouring matter present.