XJj INTRODUCTION. 



of this research, in any instance been conclusively determined. It is true 

 that in certain instances differences have been noted, but these, as a rule, 

 could readily be accounted for without the assumption of chemical differ- 

 ences inherent in the molecules; and in the exceptional cases it is not certain 

 whether we are dealing with normal individuals or with several individuals 

 or with contaminated individuals, etc. For instance, the fact that the egg- 

 white of the eggs of certain species remains perfectly clear upon boiling, 

 while that of other species becomes opaque, might be taken as meaning 

 a difference in chemical composition, but the difference has been shown 

 to lie in the different amounts of alkali and saline present. That the egg- 

 albumin of the chicken, pigeon, and seed-crow has been crystallized, while 

 the experimenter has not been successful with the egg-albumin of other 

 species, may imply nothing more than different conditions extrinsic to the 

 molecules. The caseinogens of woman's and cow's milk are looked upon 

 as being not identical, yet the primary dissociation products show a great 

 similarity and the elementary analyses of the caseinogen of the cow, goat, 

 and rabbit are identical. The centesimal analyses of corresponding albu- 

 mins and globulins have failed to show any positive differences. Oppen- 

 heimer states, from the results of a recent study of the serum albumins of 

 man, the horse, and ox, that serum albumin is a uniform and specific sub- 

 stance, and that the elementary analyses point to one serum albumin. In 

 the case of the hemoglobins the differences in the analyses of the hemoglo- 

 bins of different species are not, with rare exceptions, greater than those of 

 the hemoglobins from different individuals of the same species. Osborne's 

 assertion that the glutenins of wheat and rye are not chemically alike is 

 founded on the fact that "wheat flour readily yields gluten consisting of glia- 

 din and glutenin, whereas rye flour does not. " (Extract from a letter from 

 Professor Osborne in response to an inquiry for data justifying his statement.) 

 Crystallographic differences believed by Giirber to be shown by the 

 serum albumins of the horse and rabbit were disproved by his pupils; the 

 crystals of lactalbumin closely resemble or are even identical with those 

 of serum albumin. The statements made from time to time that the hemo- 

 globins of different species can be distinguished by differences in crystalline 

 form have been contradicted, and have been based upon manifestly inade- 

 quate investigation. Positive differences have been noted, but the differ- 

 ences between the forms of the crystals of different species have not been 

 greater than the differences in the forms obtained from specimens of blood 

 from individuals of the same species that have been recorded by the same 

 or by different investigators. Preyer, in his well-known monograph Die 

 Blutkrystalle, Jena, 1871, refers in a table (see Chapter V) to the crystalline 

 forms of the hemoglobin from 44 species, and with rare exceptions the 

 crystals are described as prisms, rods, plates, and needles, and occasionally 

 as six-sided rods or plates. All of the crystals, when classified according to 

 system, have been assigned to the rhombic system, except one, and possibly 

 three other instances where they are classified as hexagonal. Indeed, in 

 those exceptional instances we have proven that the crystals do not belong 

 to the hexagonal system. While seeming differences have been recorded 



