ALBUMINS OR PROTEINS. 141 



and reptiles, from the pancreas, from the gastric juice, from the thyroid 

 gland, from suprarenal glands, and from muscles. Nucleoproteids have 

 also been found in tumors. The nucleoproteid of yeast has been much 

 studied on account of the ease with which its nucleic acid is obtained. 

 We must also call attention to the presence of nucleoproteids in the 

 vegetable kingdom. 



Oxy-hemoglobin likewise belongs to the group of proteids. It is 

 composed of globin and hematin. We have met the former while dis- 

 cussing the histons. Oxy-hemoglobin contains, according to the inves- 

 tigations of Fr. N. Schulz, 1 about 4-5 per cent hematin. We do not, at 

 present, know whether different kinds of animals possess different kinds 

 of hemoglobin; in fact, we are not at all certain that one and the same 

 species of animal has a uniform hemoglobin. The crystalline form of the 

 hemoglobin is of little value. The investigations of the globin portion 

 have also been of little service. The hemoglobin from the horse has been 

 most thoroughly studied. The decomposition of the hemoglobin from 

 the dog gave corrresponding amounts of amino acids. The second com- 

 ponent, hematin, seems to have constant properties, irrespective of the 

 animal from which it is obtained. We shall devote more attention to 

 hematin when we discuss the composition of blood. We shall also have 

 to consider then the part hemoglobin plays as a carrier of oxygen and 

 carbon dioxide. 



The glucoproteids form the third subdivision of the proteid group. 

 They are composed of a protein and a carbohydrate complex. We have 

 already met them in our discussion of the carbohydrates, 2 and have 

 seen that glucosamine is produced by the hydrolysis of the ordinary 

 mucins, while galactosamine is obtained from the mucin of frog-spawn. 

 These are the only carbohydrates that have been positively isolated from 

 the glucoproteids. It is, indeed, very questionable whether the carbo- 

 hydrates mentioned pre-exist as such. The whole group of glucoproteids 

 is still very indefinite. While it is comparatively easy to decompose the 

 nucleoproteids and hemoglobin into their albuminous and non-albumi- 

 nous constituents, this does not hold with the glucoproteids. The carbo- 

 hydrate group is only split off by boiling with mineral acids or by the 

 action of alkalies. It is, of course, possible that the glucoproteids are* 

 true albuminous bodies, differing only from the other proteins, in that 

 more carbohydrates take part in their formation. Certain of the ordi- 

 nary albumins may indeed really belong to this group. If this be true, 

 we would then have all shades of proteins, some with considerable car- 

 bohydrates others with less, and some which do not contain any carbohy- 

 drate at all in the molecule. 



1 Fr. N. Schulz: Z. physiol. Chem. 22, 449 (1898). 



2 Cf. pp. 20 and 25. 



