194 THE AMERICAN MONTHLY [Jul 



tals from dog's blood is suggested by Dr. S. Waterman. 

 Defibrinate and mix water in equal parts to each volume 

 of blood. Add to four volumes of the blood solution one 

 volume of alcohol. Set the mixture to rest for twenty- 

 four hours at a temperature of 0° or less. The crystals 

 formed are filtered off, pressed, dissolved in the smallest 

 quantity of water, say 25 to 30 per cent, exposed to a 

 temperature of 10°, and left undisturbed for twenty-four 

 hours. The whole solution will be found converted into 

 a crystallized mass. 



Hemoglobin. — The production of haemoglobin crystals 

 is surrounded at times with more or less difficulty, owing 

 to the rapidity with which the haemoglobin decomposes. 

 A simple method is to allow the blood to coagulate, ex- 

 press the serum, and separate the fibrin by filtration. 

 Through this solution pass a current of oxygen for half- 

 an-hour, and then carbonic acid gas for ten or fifteen min- 

 utes. Crystals may be readily obtained from the blood 

 of the dog and other animals by adding alcohol in small 

 quantities during the passage of the gas currents. 



Magnesium. — As an illuminant for photo-micrography 

 this is not a new idea. It was used for this purpose by 

 Dr. R. L. Maddox as far back as 1864, but owing to the 

 expense of its production it never became really popular. 

 Magnesium is prepared commercially from the melted 

 chloride of electrolysis, or by metallic sodium, and, when 

 heated either in air or oxygen it first glows and then 

 burns with a bluish-white dazzling flame. The experi- 

 ments of Bunsen and Roscoe have shown that the sun at 

 its zenith has only 36 6 tmies more chemical brightness 

 and 524*7 times more visual brightness than magnesium. 

 It is therefore specially suitable for photographic pur- 

 poses, and now that the price of the metal, either as bar, 

 wire, ribbon, or powder is so low, there is every induce- 

 ment to the photomicrographer to call in its aid, 



