SINCE PREYER'S INVESTIGATIONS. 129 



pig crystals from one or both may appear, but the process is invariably 

 retarded, sometimes to a marked degree. If crystals of both kinds of oxy- 

 hemoglobin are deposited, those of one usually begin forming some time 

 before those of the other, and the crystallization of one may be seemingly 

 complete before crystals of the other are seen. 



The interesting observation was also made that the typical forms of 

 the crystals of certain kinds of oxyhemoglobin may be modified or com- 

 pletely changed when the bloods of two species are mixed. Thus, if to the 

 blood of the rat there be added a definite percentage of the blood of the 

 guinea-pig, crystals of the rat's oxyhemoglobin may appear in unaltered 

 form, but most, if not all, of those from the guinea-pig's blood are changed; 

 in fact, if any perfect tetrahedra are found, they will have been formed at 

 the very end of the crystallization. If the proportions of the mixture be 

 properly modified, not a single crystal of what can be identified as rat's 

 oxyhemoglobin will appear, and all the crystals will be modified tetrahedra, 

 spindles, and transitional forms between these. The spindles resemble Char- 

 cot's crystals in form, but not in color; they vary in size, some being very 

 large, and some may have small spindles attached to them; they can be 

 obtained having sharp edges if crystallization has not been too rapid. 



This complete change in the form of the crystals of oxyhemoglobin 

 when the bloods of two species are mixed, and the spindle-shaped form of 

 the crystals, are, he believes, unique facts in the crystallography of this 

 most important substance. (See Halliburton, page 115.) 



Moser (Vierteljahresschr. f. gerichtl. Medizin, 1901, xxn, 44) asserts 

 that differences in crystalline form afford a positive means of recognition of 

 the origin of the blood, and that positive distinction can be made between 

 human and animal blood. He examined blood stains of the fresh blood 

 of man and 10 species of mammals and fish, and gives drawings of their 

 appearance under the microscope. From the differences in shapes he infers 

 differences in crystallization, which he reasons indicate differences in chem- 

 ical constitution. No descriptions of the crystallographic or optical char- 

 acters are given, and, as differences in the shapes of the crystals do not 

 necessarily imply differences in crystal system, his conclusions are based 

 upon insufficient data. Bonnel (These de Paris, 1903; Jahr. ii. d. Fort. d. 

 Thierchemie, 1903, xxm, 182) showed, however, that the method of Moser 

 is not worthy of recommendation because by this method he obtained from 

 human blood crystals of different shapes. Friboes (Archiv f. ges. Physiol- 

 ogic, 1903, xcvni, 434) also found that human blood treated in the manner 

 described by Moser crystallizes in various forms. He notes that the bloods 

 of certain animals show crystalline shapes which, with the exception of the 

 bat and the goat, are distinguishable from human blood. He describes the 

 different forms of the crystals he observed, but gives no definite crystallo- 

 graphic data by which they may be recognized. (See Chapter VII.) 



In experiments with the blood of the horse, Uhlik (Archiv f. ges. Phys- 

 iologie, 1904, civ, 64) found that as putrefaction progresses the usual rhombic 

 crystals of oxyhemoglobin are replaced by hexagonal, holohedral crystals 

 of reduced hemoglobin. Table 34 indicates the influences of the condition 

 of the blood and temperature upon crystallization. 



