PHYSIOLOGY — REICHERT AND BROWN. 219 



from which Hne-drawings, to illustrate the text, will be made. Much calcu- 

 lation and study from these notes must be done before the final results of 

 the research can be definitely formulated. 



From a preliminary review of these results certain facts stand out very 

 prominently : 



(i) The constancy of generic characters in the crystals. For instance, 

 the genera that have been represented by a considerable number of species, 

 as Felis, Canis, Papio, Bquus, etc., show in each case constancy in the char- 

 acters of the crystals in each genus, with marked differences both in axial 

 ratios and in crystal systems between the crystals from the different genera. 

 When the characters of the crystals from any one of these genera are tabu- 

 lated, they at once recall to the mineralogist the crystallographic groups of 

 minerals. The crystals of the genus Pelts are as strictly isomorphous as 

 those of the calcite group of the rhombohedral carbonates. As an example 

 of the individuality of these generic characters, the following example may 

 be cited : A sample of blood, marked as that of a certain species of baboon, 

 was received from one of our zoological gardens. Upon making preparations 

 and examining the crystals, it was at once evident that they did not corre- 

 spond to any species of baboon thus far examined, nor did they show the 

 characters of the crystals of this genus. They were identified by their crys- 

 tallographic characters as belonging to the cats (genus Pelis), but not to 

 any species thus far examined. Inquiry at the zoological garden from 

 which the blood was received showed that the animal recorded as being 

 subjected to a postmortem examination on the date when the blood was 

 collected was a species of cat (genus Pelis), but not one of which we had 

 previously examined the blood. 



(2) Specificity in the crystals of a genus. The crystals of different species 

 of a genus can usually be distinguished from each other by definite differences 

 of angle, when they are favorable for good measurement, while preserving 

 their isomorphous character as belonging to a definite genus. From the 

 difficulty of measurement in many cases it is hard to give these differences a 

 quantitative value, but the variation in habit of the crystals and their mode 

 of growth will often show specific differences. 



(3) The occurrence of several types of crystals of oxyhemoglobin in 

 many species. The oxyhemoglobin of some of them is dimorphous, crystal- 

 lizing in two systems, or even trimorphous in many cases. Here it is gener- 

 ally seen that the crystals first formed crystallize in a system of a lower 

 grade of symmetry than those formed later. When several types of crystals 

 occur in the species of a genus, they may each be arranged in isomorphous 

 series. The explanation of these observations seems to be indicated by the 

 results obtained. 



(4) The constant recurrence of certain angles, either plane or dihedral, 

 in oxyhemoglobin, hemoglobin, and the " methemoglobins" of various spe- 

 cies, even when widely separated zoologically and when the crystals belong 



