INTRODUCTION. XV11 



Park, Washington, D. C., and Dr. W. Reid Blair, pathologist of the New 

 York Zoological Park. To Dr. John R. Mohler, chief of the division of 

 pathology, U. S. Department of Agriculture, Washington, D. C., we are 

 especially indebted. 



We have had at our disposal specimens from about 200 species of 

 mammals, most of them received from the zoological gardens, and usually 

 in various stages of putrefaction. It would have been advantageous in 

 many ways if in every case we had had not only fresh blood, but also blood 

 from healthy animals and in larger quantities. Yet in so far as the speci- 

 ficity of the crystals is concerned we believe that neither the presence of 

 putrefactive processes in the blood nor diseased conditions generally have 

 any important influence. The greatest disadvantage of putrid blood con- 

 sists in a greater unstability of the preparations and in the difficulty of 

 securing some of the more evanescent forms of oxy hemoglobin. Owing to 

 an absence of preliminary knowledge of the peculiarities of the hemoglobins 

 of different bloods as regards the degree of crystallizability, or to the exceed- 

 ingly small quantities we usually had to work with, or to extreme putrefac- 

 tion or other conditions over which we had no control, we occasionally failed 

 absolutely to obtain any evidence of crystallization, and many of our speci- 

 mens were lost owing to the perishability of the crystals of certain species 

 or to the very pressing demands of teaching. In fact, what work we have 

 accomplished has been through the utilization of such scattered hours as 

 could be taken from the exacting requirements of the class-room and of 

 routine work. Moreover, owing to the extreme solubility of many of the 

 crystals, our investigations were largely limited to the cooler months, and 

 much of our work was done at temperatures at or near the freezing-point. 



It was our expectation to include in this memoir the results of a few 

 preliminary studies of certain other corresponding vital substances, espe- 

 cially of plant proteins. Our data are not, however, more than sufficient 

 at present to justify the announcement that we believe that the zoological 

 distinctions we have found to be shown by hemoglobins will be demon- 

 strated in other primary organic substances. 



This research has proved of exceptional fertility and importance in 

 crystallography. It has brought to light the most extraordinary isomor- 

 phous series known; and it has yielded not only the crystallographic data 

 we have recorded in this memoir, but also much that has been omitted 

 because chiefly of its essentially technical character. This latter we will 

 include in a separate memoir in the near future. 



We have not in the present memoir attempted to support Dr. Reich- 

 ert's hypothesis beyond the mere presentation of our discoveries. The 

 problems pertaining to the origin of species, heredity, mutations, sex, and 

 the influence of food and environment are of such extraordinary importance 

 as to have engaged the master minds in biological inquiry, and the task of 

 presenting so important a matter in the form which we believe is neces- 

 sary to be acceptable to the critical student has seemed too formidable 

 for us to undertake at present. After all, perhaps, it is sufficient and better 

 that we merely state the important hypothesis upon which we have worked, 



