SINCE PREYER'S INVESTIGATIONS. Ill 



or an aqueous solution of the hydrochlorate of chinolin, and by its aid pre- 

 pared crystals of pig's blood. He notes that Hiifner previously found that 

 the blood of the pig mixed immediately with one-third of its volume of a 

 1 per cent alcoholic solution of chinolin crystallizes beautifully when sub- 

 jected to cold, the mixture after several days containing a mass of needles 

 and plates which liquefied within an extremely short time when exposed 

 at room temperature under the microscope. Otto used chinolin solutions 

 and blood in varying proportions, as follows: (a) 100 c.c. of blood, 40 c.c. of 

 1 per cent chinolin hydrochlorate solution, and 30 c.c. of alcohol; (b) 100 c.c. 

 of blood, 30 c.c. of chinolin solution, and 30 c.c. of alcohol; (c) 100 c.c. of 

 blood, 25 c.c. of chinolin solution, and 25 c.c. of alcohol. The mass of crys- 

 tals which had collected during 8 days was washed on a filter-paper with 

 alcohol (diluted 4 times) and then dissolved in a small quantity of water. 

 Adding to this solution one-eighth its volume of alcohol, the mixture was 

 again placed in the cold, whereupon crystals sometimes separated within a 

 few days. As a rule, the second crystallization failed to occur, and instead 

 a mass separated out in from 8 to 14 days, which was found to be met- 

 hemoglobin. 



The unsatisfactory results of this method led Otto to adopt what is 

 practically the Hoppe-Seyler method : The blood was diluted with salt 

 solution and stood in a cylindrical vessel for two days. The corpuscles were 

 collected and dissolved in the smallest possible quantity of water at 50, 

 300 c.c. of water being sufficient for the solution of the corpuscles from 1 

 liter of blood. Owing to the unusual solubility of the crystals of pig's blood, 

 which liquefy at room temperature, it is very important, as Otto states, to 

 avoid an excess of water in dissolving the corpuscles. The solution is filtered, 

 cooled, mixed with cold absolute alcohol in the usual proportion of 4:1, 

 and then subjected to cold. As a rule, after only one day a thick mass of 

 fine, bright-red needles was found at the bottom of the cylinder. For the 

 purpose of recrystallization, the crystals were collected upon a folded filter- 

 paper, washed, and crystallized 3 times with dilute alcohol in the ice-chest. 

 He prepared dog's crystals in the same way. The crystals were finally spread 

 upon plates and dried under a bell-jar over sulphuric acid in the cold. 

 The crystals of pig's blood thus prepared were then powdered, heated to 

 115, and subjected to a stream of hydrogen, when they gave off 5.9 per cent 

 of water. Those of the dog similarly treated lost only 4 per cent of water. 

 Both kinds of crystals were subjected to elementary analyses (page 71). 



Otto also analyzed the methemoglobin of the pig. Studies were also 

 made of the extinction coefficients (page 77) and of the oxygen capacities. 

 The crystals were determined by the spectroscope to be oxyhemoglobin. 

 In a later research (Archiv f. ges. Physiologic, 1883, xxxi, 240) Otto pre- 

 pared crystals of horse's blood, which he also subjected to elementary 

 analysis and spectroscopic examination. In his former investigation he 

 determined that the extinction coefficients of the oxyhemoglobin of the pig 

 and dog are the same (1.33), and in this inquiry* the extinction coefficient 

 of horse oxyhemoglobin was found to be 1.352. His elementary analyses 

 are given on page 71. He also noted the observation of Hoppe-Seyler 



