CHAPTER VI. 



THE PREPARATION AND CRYSTALLOGRAPHY OF HEMOGLOBINS 

 SINCE PREYER'S INVESTIGATIONS. 



Since the appearance of Preyer's monograph very little progress has 

 been made either in the methods of preparing the blood crystals or in the 

 study of their crystalline characters, although much has been added to our 

 knowledge of hemoglobin in certain other directions. Such simple methods 

 as have been described for preparing crystals in small quantities, together 

 with Hoppe-Seyler's method for preparing them in large quantities, have 

 proved so satisfactory for general laboratory purposes that there has been 

 little encouragement to seek new processes; while Preyer's long list of 

 crystals from different species, and the assignment of all of them to the 

 rhombic system, except those of the squirrel, seem to have discouraged 

 research along the lines of crystallography. In fact, with rare exceptions 

 when crystals from a new species have been isolated, the observer has been 

 content without further inquiry to record them as being rhombic. We are 

 therefore now, so far as the crystallography of hemoglobin is concerned, 

 virtually where we were when Preyer's monograph was published (1871). 



The method of furthering crystallization by the putrefactive process, 

 already pursued by a number of observers, was adopted by Gscheidlen 

 (Archiv f. ges. Physiologie, 1878, xvi, 421), who placed defibrinated blood 

 in a glass vessel with little air, and kept it in an incubator until the absorp- 

 tion spectrum showed the absence of oxyhemoglobin. When a drop of this 

 blood was placed on an object-glass, allowed to evaporate slightly, and then 

 covered with a cover-glass, crystals appeared under the eye of the operator. 

 From dog's blood which had stood for several days in the incubator he 

 obtained crystals from 3 to 4 mm. long. The rapid crystallization of the 

 blood thus prepared he found to be due to putridity, since blood kept in 

 sterilized vessels under the same conditions showed far less power of crys- 

 tallization. In guinea-pig's blood kept in the incubator with the admission 

 of air he found not only large tetrahedra, but also rhombic plates and 

 prisms. By this method Gscheidlen prepared crystals from the blood of 

 the dog, guinea-pig, sheep, bullock, rabbit, and goose. He also noted that 

 blood kept in hermetically sealed tubes for several years crystallized in a 

 short time upon exposure to the air. The readiness with which putrid blood 

 crystallizes had already been noted by Schmidt, Bottcher, Blebs, and others. 



A method by Kiihne and Gamgee (Gamgee's Physiological Chemistry, 

 1880, 87) is as follows: 500 c.c. of defibrinated dog's blood are treated 

 with 31 c.c. of ether and the mixture shaken for some minutes. It is then 

 set aside in a cool place. After a period varying from 24 hours to 3 days 

 the liquid becomes converted into a thick magma of crystals. The crystals 



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