SINCE PREYER'S INVESTIGATIONS. 109 



the rubber tube is broken off, and by alternate cooling and heating of the 

 flask sufficient alcohol is introduced so that the solution contains about 

 25 per cent of alcohol. The free end of the rubber tube is now closed by a 

 screw clip and glass stopper and the solution is subjected to a temperature 

 of 5 to 10. After 12 to 24 hours the reduced hemoglobin has crystallized 

 into glittering plates and prisms. When examined under the microscope 

 at in the mother-liquor, the crystals for the most part appear as 6-sided 

 plates, of which some were from 2 to 3 mm. in diameter. In the micro- 

 spectroscope every crystal showed only the one band of reduced hemo- 

 globin. The prismatic crystals are doubly refracting. The color of the 

 larger plates is a beautiful violet red; the smaller thin plates appeared 

 greenish in transmitted light. The crystals were very sensitive to oxygen 

 and warmth. At room temperature they quickly melt, and as quickly they 

 lose their violet color and show by the microspectroscope the bands of 

 oxy hemoglobin. In absolute alcohol they remain unchanged, at least in so 

 far as their form is concerned. If the hemoglobin solution is mixed too soon 

 with alcohol, before the bacteria have taken up the last traces of oxygen, 

 both reduced-hemoglobin and oxyhemoglobin crystals are formed. 



Besides the differences they describe in the color and spectroscopic 

 behavior Nencki and Sieber also make note of differences in the forms of 

 oxyhemoglobin and reduced hemoglobin. From horse's blood they obtained 

 oxyhemoglobin in long 4-sided columns, and the reduced hemoglobin in 

 thin 6-sided plates which are more soluble in water than the oxyhemoglobin. 

 In horse's blood which has decomposed in well-closed or sealed vessels, 

 the reduced hemoglobin separates as a thick crystal pulp on the addition 

 of alcohol after standing several hours at a temperature under 0. 



Gamgee (Schafer's Text-book of Physiology, 1898, 1, 232) gives a 

 method for preparing reduced hemoglobin which he states he employed 

 20 years previously, and which seems to him to possess some advantages: 

 A magma of pure oxyhemoglobin crystals and a small quantity of the 

 mother-liquor are placed in a glass tube so as nearly to fill it, and the tube 

 sealed and heated for some days in an incubator at about 35 and then set 

 aside in a cool place. After some weeks of exposure at winter temperature 

 crystals of reduced hemoglobin will be found. Crystals of reduced hemo- 

 globin have also been prepared by Ewald, Frey, Uhlik, Copemann, Dono- 

 gany, and others, as will be shown by subsequent references. 



The changes in solubility of crystals of hemoglobin that are caused 

 by alcohol were studied by Struve (Ber. d. d. chem. Ges., 1881, xiv, 930; 

 Jour. f. prakt. Chemie, 1884, xxix, 304), who found that fresh crystals 

 placed in strong alcohol immediately became darker, without change of 

 form, and insoluble in water. Upon treating crystals with dilute alcohol, 

 they became faintly yellowish or completely decolorized. These and other 

 phenomena led Struve to resurrect the long since abandoned view that 

 the blood crystals are composed of a colorless albuminous substance which 

 is stained or colored mechanically. 



After leeches have sucked blood and crystallization has begun, speci- 

 mens of hemoglobin crystals may be obtained from time to time, as shown 



