SINCE PREYER'S INVESTIGATIONS. 123 



1894, 113) and others for crystallizing serum albumin, has been used by 

 Dittrich (Archiv f. exper. Path. u. Pharm., 1892, xxix, 250) and others for 

 preparing crystals of hemoglobin. Owing to the rapid conversion of hemo- 

 globin into methemoglobin by this process, Dittrich used it also to prepare 

 the latter. The blood of the horse was subjected to the Hoppe-Seyler 

 process for preparing the blood-corpuscle pulp. The corpuscles were then 

 dissolved in ether, the solution filtered, and then mixed with two volumes 

 of a cold saturated solution of ammonium sulphate, filtered again, and then 

 placed in flat vessels in the cold. Generally within 24 hours crystallization 

 begins, but occasionally only after 2 to 3 days. The crystals could be recog- 

 nized microscopically in transmitted light as glittering elongated prisms 

 or broad plates. The crystals of the first crystallization were not pure; 

 moreover, the mother-liquor contained, besides crystals, an amorphous 

 precipitate which often could be separated only by repeated recrystalliza- 

 tion. Generally a separation of "globulites" and spherocrystals preceded 

 the formation of crystals. The most of the crystal mass of oxy hemoglobin 

 changed on standing in the air, and through the processes of recrystalliza- 

 tion, gradually and completely into methemoglobin. No further change, 

 for example the formation of hematin, took place. The crystal pulp, 

 recrystallized several times from ammonium sulphate solution, was finally 

 pressed between absorbent paper, and when dry was saved in this condi- 

 tion. This method of production of methemoglobin renders superfluous 

 the use of ferricyanide of potassium or any other agent, the ammonium 

 sulphate in large quantities being sufficient to change the hemoglobin to 

 methemoglobin. Finally, the crystal pulp with the contained ammonium 

 sulphate is permanent, and its solubility is not lost. If, however, the 

 preparation is completely dried over sulphuric acid in vacuo, the largest part 

 of the methemoglobin is changed to an insoluble modification. 



Schulz (Zeit. f. physiol. Chemie, 1899, xxiv, 454) used essentially the 

 same process for preparing oxyhemoglobin for his studies of globin. Horse's 

 blood was rendered incoagulable by ammonium oxalate, the corpuscles 

 were collected by decantation and then diluted with 2 volumes of water. 

 If the solution obtained in this way is mixed with a like volume of cold 

 saturated ammonium sulphate solution, there is formed an abundant 

 precipitate which consists essentially of fibrinogen and serum globulin. 

 The precipitate after a time becomes so compact that it can be separated 

 by filtration, but, since the hemoglobin begins to crystallize immediately, 

 filtration is rendered difficult because the pores of the filter become quickly 

 clogged. In the completely clear filtrate crystallization soon begins, but 

 the quantity thus obtained is small because of the separation on the filter. 

 If the hemoglobin solution and the ammonium sulphate solution are warmed 

 to 40 before mixing, the separation of crystals takes place less quickly, 

 so that the filtrate obtained is almost completely free from blood-coloring 

 matter. If, on the other hand, both solutions are cooled in an ice-chest 

 before the mixing, and the solution after the mixing is allowed to stand 

 until the albuminous precipitate has completely settled, the crystallization 

 of the hemoglobin is almost completely prevented before filtration. If the 



