218 CRYSTALLOGRAPHY OF HEMOGLOBINS OF THE RODENTIA. 



The rats examined (genus Mus) form a distinct group, with crystals 

 that closely resemble each other in form, but vary very much in habit. 

 An examination of these crystals will at once show that the four kinds of 

 rats examined may be arranged in two series, the Norway rat and the white 

 rat being evidently the same species, the albino variety, however, varying 

 somewhat from the typical Norway rat. On the other hand, the crystals 

 of the blood of the black rat and the Alexandrine rat closely resemble each 

 other, but differ markedly in habit from those of the Norway and white 

 rats. The crystals of the Norway and white rats form rapidly, and are more 

 insoluble than those of the black and Alexandrine rats; they are much 

 smaller, and hence paler in color, and they show a rather stronger double 

 refraction than those of the black and Alexandrine rats. These latter 

 crystals are larger and more regularly formed and do not twin so constantly 

 as those of the Norway and white rats. 



In the monoclinic crystals of the beaver, the muskrat, and the por- 

 cupine considerable resemblance is to be seen, although each animal belongs 

 to a separate family; the distinctions between the species will be readily made 

 out on comparing the photographs of the crystals, and their descriptions, as 

 given under each species. It will be noted that the prism angles of these 

 three species also run near 60, which appears to be common in the rodents. 



The guinea-pig and capybara differ from all of the other rodents exam- 

 ined in having distinctly pyramidal, rather than prismatic or tabular crys- 

 tals. The crystals of the guinea-pig are orthorhombic sphenoidal, while 

 those of the capybara are tetragonal. 



The crystals from the blood of the common rabbit and the Belgian 

 hare closely resemble each other, and, as may be seen from the axial ratios, 

 the extinction angles, and the prism angles of the monoclinic form, these 

 two species are closely related. Here again the prism angle approaches 60. 

 The data in regard to the Belgian hare are not complete, however, so that 

 the comparison is not perfect. In solubility, and even in the form of their 

 crystals, these two species of Lepus differ very widely from the other rodents. 

 Whereas the crystals of the rodents in general are rather insoluble, those 

 of the rabbit and hare are very soluble, and they must be examined in cold 

 weather or they will dissolve while under investigation. 



RODENTIA. 

 EUROPEAN RED SQUIRREL, Sciurus vulgaris. Plate 45. 



Two specimens of blood were examined, one from an animal purchased 

 from a dealer and bled in the laboratory, and one from an animal that 

 died at the Philadelphia Zoological Gardens. The latter specimen con- 

 sisted of only a small amount of fluid blood, and was in a very putrid con- 

 dition. In both cases the oxalated blood was laked and (in the case of the 

 fresh blood) centrifugalized, and the slide preparations made as usual. 

 Crystals formed very readily at room temperature, and they were quite 

 insoluble, showing no tendency to dissolve. Good photomicrographs were 

 obtained within 2 or 3 hours after making the preparations. In both cases 

 the blood yielded crystals of oxy hemoglobin. The crystals obtained from 



