168 The Microscope. 



fifteen to thirty minutes. Crystals may thus be obtained from the 

 blood of the guinea-pig, the squirrel and the cat. Dog blood requires 

 more^ time. Most time is required by the blood of man and the 

 hare. No crystals are in this loay obtainable from the blood of the 

 swine or the frog. 



Another practical way to obtain crystals is to employ dog blood. 

 Defibrinate and mix water in equal parts to each volume of blood, 

 and add to four volumes of the blood solution one volume alcohol. 

 Set the mixture to rest for twenty-four hours at a temperature of 0"^ 

 or less. The crystals will form, are filtered off, pressed, solved in 

 the smallest quantity of water, say 25 to 30 per cent., exposed ta 

 a temperature of 0^. This solution is mixed again with one-fourth 

 of its volume of alcohol at a temperature of 0°, or perhaps better 

 at 10 to 20'^, and left undisturbed for twenty-four hours. The 

 whole solution is converted into a crystalline mass, without the 

 freezing of the water. 



There are other methods to obtain the blood crystals in large 

 quantities, but this will do for the present. More detailed accounts 

 can be found in Preyer's work, "Die Blutceyatallo von W. Preyor, 

 Jena." 



PRODUCTION OF BLOOD CRYSTALS IN SMALLER QUANTITIES. 



1. Warming the blood up to a temperature of 60°, we obtain 

 a dark-colored solution, each drop of which, on slow evaporation, 

 will yield crystals. In this way we may obtain crystals from blood 

 of the guinea-pig, and from horse blood. (Max Schulze.) 



2. By adding a small amount of ether to the cold blood 

 solution (of dogs), and then gradually warming, and afterwards- 

 cooling at a low temperature, furnishes the finest crystals in the 

 shortest period of time. (Preyer.) 



3. The constant electric current carefully applied will produce 

 crystals from the blood of man, cats, dogs and guinea-pigs. 

 (Uollet.) 



4. When a glass balloon is filled with dog's blood, into which 

 air, highly heated, is introduced, and is left to stand at 30°, under 

 exclusion of air, it is found after the lapse of four to six weeks that 

 the air above the blood has lost nearly three per cent, of oxygen and 

 gained an equal percentage of carbonic acid. An enormous quantity 

 of crystals of hemoglobin has formed in the meantime. (Pasteur.) 



5. By directing a current of air (previously passed through a 

 small quantity of chloroform) through defibrinated blood, every 

 drop furnishes crystals on evaporation. 



