THE CHEMICAL DETECTION OF BLOOD 361 



According to Reichert, the degree of modification of crystal form 

 induced by admixture of two bloods depends very greatly upon the 

 proportion in which they are mixed. 



In view of these facts there can be little doubt that the nature of 

 the milieu in which crystallization occurs does play an important part 

 in determining the form of the crystals which are deposited, and having 

 regard to the known individuality of the plasma from different bio- 

 logical species, it would appear unnecessary to seek further for the 

 origin of the differences in crystal form of the oxyhemoglobins derived 

 from blood of different species of animals. 



In this way we can also interpret the changes in crystal-form which 

 Halliburton observed to result from repeated Recrystallization of 

 hemoglobin, for as Wichmann and more recently Katz have shown, 

 the crystalline proteins swell in, or absorb the surrounding fluid 

 menstruum in a manner analogous to the swelling of jellies. A number 

 of recrystallizations are therefore required to remove completely traces 

 of the original menstruum in which crystallization occurred. 



Bradley and Sansum believe that the hemoglobins from different 

 animals are antigenically different, because guinea-pigs sensitized to 

 ox- or dog-hemoglobin failed to display Anaphylactic Shock, or reacted 

 but slightly to hemoglobins of other origins, while they reacted strongly 

 to the hemoglobin with which they were sensitized. As the hemo- 

 globin preparations employed by Bradley and Sansum were admittedly 

 (with the exception, they believe, of dog-hemoglobin) not free from 

 contamination by serum, the interpretation of these results is open to 

 serious question. Doubt is especially thrown upon this evidence for 

 the specificity of hemoglobins from different species by the fact that 

 the animals sensitized to the purest preparation of hemoglobin em- 

 ployed, that of the dog, reacted strongly, not only to dog-hemoglobin, 

 but also to dog-serum. Observers are not all agreed that pure hemo- 

 globin is antigenic; its protein component, globin, certainly is not, 

 and having regard to the investigations of Wichmann and Kat, 

 cited above, revealing the marked ability of crystalline proteins to 

 absorb the menstruum from which they are deposited, and to the 

 observation of Schulz and Zsigmondy that Egg-albumin must be 

 recrystallized from 3 to 6 times in order to remove appreciable con- 

 tamination by other proteins, we may infer that in all probability 

 the specificities demonstrated by Bradley and Sansum are serum- 

 specificities and not hemoglobin-specificities. 



THE CHEMICAL DETECTION OF BLOOD. 



The chemical detection of blood and identification of blood-stains 

 is often of the very gravest medicolegal import. The older methods 

 of detection depended upon microscopical identification of blood- 

 corpuscles, and, of course, a very slight degree of putrefactive change, 

 or the drying of a blood-stain upon a garment rendered the detection 



