96 INVESTIGATIONS OF PREYER 



many thicknesses of filter-paper. On the addition of 20 c.c. of 90 per cent 

 alcohol to 100 c.c. of the filtrate a firm crystalline pulp is soon formed, which 

 is collected on a filter and washed, at first with a mixture of 4 parts of 

 water and 1 part of alcohol and then with iced water. According to this 

 method fully 5 grams of pure recrystallized dry hemoglobin are obtained. 

 Recrystallization yields, according to Kiihne, a pure preparation only if 

 the first crystallization contained no corpuscles. This method is somewhat 

 troublesome. The addition of crystallized bile, as well as of acetic acid, 

 Preyer believes, may give rise to decompositions of the hemoglobin. 



(V) Defibrinated dog's blood is mixed with about its own volume of 

 distilled water, and to every 4 volumes of the blood solution there is added 

 1 volume of alcohol. The mixture is left for 24 hours at a temperature of 

 0, or lower. The crystals that have separated are collected on a filter, 

 pressed, dissolved in the smallest amount of water at 25 to 30, cooled to 

 0, the solution mixed with one-fourth its volume of alcohol and left stand- 

 ing for 24 hours at 0, or better at 10 to 20. The entire fluid becomes 

 converted into a crystalline mass without freezing. This recrystallization 

 can often be repeated. 



From the bloods of several rodents, for example the guinea-pig and 

 the rat, blood crystals were obtained on the addition of pure water after 

 defibrinization, because the crystals are not soluble in cold water, yet they 

 can also be recrystallized by dissolving in water at 30 and cooling, or 

 evaporating over sulphuric acid in a rarefied atmosphere, and they can be 

 dried at without decomposition. (Method of Hoppe-Seyler.) 



Preyer occasionally observed that fresh defibrinated blood of the dog, 

 after dilution with pure water, yields the most beautiful crystals upon 

 evaporation. Once he mixed 5 c.c. of blood with 4 c.c. of distilled water, 

 poured the solution into a shallow porcelain vessel, and let it stand over 

 night at a temperature between 19 and 20. On the dried marginal por- 

 tions of the solution, after about 15 hours, exceptionally beautiful crystals, 

 5 to 6 mm. in length and intensely red, were formed. Yet he did not 

 always succeed in producing blood crystals from dog's blood in this way. 



Of the five methods described, the last, according to Preyer, is decidedly 

 the best. Yet, he states, it also needs improving. He proceeded, therefore, 

 in the production of pure hemoglobin crystals on a large scale from any 

 blood selected, in the following way: 



(VI) The blood is collected in a vessel and allowed to coagulate and 

 to stand for several hours (or, better, for a day) in a cool place. Then the 

 serum with the white corpuscles and the fat which has collected on top are 

 removed and the coagulum washed with distilled water and then cut into 

 very small pieces, and these pieces in turn are repeatedly washed with cold 

 distilled water. Then the clot is comminuted, best by freezing and reduc- 

 ing the frozen mass to powder. This powder is placed on a filter-paper and 

 washed with cold distilled water until the filtrate no longer gives a very 

 strong precipitate with bichloride of mercury. The coagula are extracted 



