322 SUMMARY AND CONCLUSIONS. 



In the great majority of cases only one preparation could be made, 

 owing to the smallness of the specimen, and in unknown bloods in such 

 cases the proper dilution to obtain the best results was not always arrived 

 at. Hence, it frequently happened that the crystals were not formed under 

 the best conditions of dilution. When a sufficient quantity was available 

 for making several preparations, the blood was crystallized at different 

 dilutions, in order that the one most favorable for normal crystallization 

 should be used in the preparation that was employed in the crystallo- 

 graphic examination. In general the whole blood was used when but a 

 single preparation could be made. When the quantity of blood was suffi- 

 cient, or its condition was such as to allow of a separation of the corpuscles, 

 we often made preparations of the corpuscles as well as of the whole blood. 

 The most concentrated solutions were obtained by separating the corpuscles 

 by centrifugalization, and using these without any added plasma or other 

 fluid. The whole blood gave a solution of medium concentration. The 

 addition of plasma or serum to the whole blood, gave dilute solutions. 

 For the very soluble forms of the hemoglobins, the corpuscles alone were 

 used; for those of moderate solubility, the whole blood was taken; while 

 for the more insoluble hemoglobins the blood was preferably diluted with 

 the plasma or egg-white. In one or another of these various ways the 

 conditions most favorable to the formation of crystals were arrived at, 

 and, as far as possible, all of the bloods examined were studied when crys- 

 tallized under the most favorable conditions. They were in general, there- 

 fore, strictly comparable. Crystallization under different degrees of dilu- 

 tion, and under different temperatures, alters crystal habit rather than 

 form, and even when the preparations were not made under the most favor- 

 able conditions for the formation of typical crystals, the crystallographic 

 characters were not altered, so far as the system, the axial ratio, and the 

 optical characters were concerned. The crystals were kept under examina- 

 tion as long as possible, in order that any different forms of the hemo- 

 globins that might develop could be studied. The specificity of the hemo- 

 globins of a genus was often seen in such different forms of hemoglobin being 

 found to run through a series of species. 



THE DIFFERENT KINDS OF HEMOGLOBINS FOUND IN THE BLOODS. 



In most cases it was possible to produce crystals of oxyhemoglobin in 

 the bloods examined, but sometimes oxyhemoglobin did not crystallize and 

 some of the other hemoglobins were observed. These were metoxyhemoglo- 

 bin, reduced hemoglobin, and methemoglobin. In many cases when a suffi- 

 cient supply of blood was available, all these substances could be prepared 

 and examined in one blood. In some cases, especially when the oxyhemo- 

 globin was rather soluble, it was found advantageous to make carbon- 

 monoxide hemoglobin in order to obtain better crystals for examination. 

 In several cases in the account of our experiments this substance has been 

 described, but it was also prepared and examined in a number of instances 

 which have not been mentioned in the above descriptions. The substance 

 called metoxyhemoglobin is, as pointed out by Menzies (Journal of Physi- 

 ology, 1894, xvu, 402), the substance usually described as " methemoglobin," 



