CHAPTER XIX. 



SUMMARY AND CONCLUSIONS. 

 MODE OF PREPARATION OF HEMOGLOBINS. 



The hemoglobins from different species examined were so prepared as to 

 be strictly comparable : 



In order that the crystals examined should be as nearly comparable 

 with each other as possible, a uniform method of procedure was adopted 

 in their preparation, which, as described under the methods of preparation 

 used in this research (page 141), consisted in adding oxalate to the blood 

 when collected to prevent coagulation, laking the blood with ether to free 

 the hemoglobins, centrifiigalizing to separate extraneous matters and get 

 a clear solution, and crystallizing on slides under covers sealed with Canada 

 balsam. This method of procedure was followed whenever it was possible 

 to do so, but it had to be modified in many cases to meet the individual 

 requirements of the specimen. The hemoglobins vary so much in solubility, 

 often even in the same genus, that when but one preparation could be 

 made, owing to the small amount of blood, it might happen that it was 

 not always crystallized at the best dilution for the blood of that particular 

 species. Still, by endeavoring to obtain the best condition of dilution, and 

 following a constant method of procedure, it was possible in most cases to 

 obtain a series of products that were strictly comparable. 



The specimens were received from various sources, mostly from the 

 Zoological Gardens, and were very variable as to quantity and condition of 

 the blood. In the majority of cases the blood was obtained when the post 

 mortem of the animal was made, and as this was usually hours, and in some 

 cases days, after death, many of the specimens were of clotted or partially 

 clotted blood that was removed from the heart and larger vessels when the 

 animal was examined; in some cases they were diluted with serum or 

 lymph ; and frequently they were in a more or less putrid condition. Gen- 

 erally, the blood was partly changed to reduced hemoglobin, but shaking 

 with oxygen or air would usually convert this to oxyhemoglobin ; or simply 

 the exposure to the air, during the evaporation of the drops of prepared 

 blood on the slide, in most cases permitted the introduction of enough 

 oxygen to make the blood yield crystals of oxyhemoglobin. In cases when 

 the blood had become putrid by exposure to air, the hemoglobin was fre- 

 quently partly changed to the acid form (metoxyhemoglobin) , and it crys- 

 tallized as such in the slide preparations. The blood was usually liquid, 

 sometimes partly or entirely clotted. The clots had to be broken up, and 

 concentrated solutions were usually obtained in such cases. When the 

 specimen was liquid, it sometimes was mainly serum or lymph, and in such 

 cases the preparations were dilute solutions. 



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