THE CHEMISTRY OF THE ANIMAL BODY. 1019 



cles of Sipunculus, while the blood of crabs, snails, and other animals (mollusks and 

 arthropods) is colored blue by a pigment, hcemocyanm, which contains copper instead of 

 iron. 



Glyco-proteids. These consist of proteids combined with a carbohydrate. They are 

 insoluble in water, but soluble in very weak alkalies. On boiling with dilute mineral acids 

 they yield a reducing substance. 



Mucins are found in mucous glands, goblet cells, in the cement substance of epithelium 

 and in the connective tissues. Of the nearly related mucoids may be named colloid, a sub- 

 stance appearing like a gelatinous glue in certain tumors ; pseudo-mucoid, the slimy body 

 which gives its character to the liquid in ovarian cysts ; and chondro-mucoid, found as a 

 constituent of cartilage. On boiling chondro-mucoid with dilute sulphuric acid it yields 

 acid-albuminate, a peptone substance, and chondroitic acid. The last is a nitrogenous 

 ethereal sulphuric acid, yielding a carbohydrate on decomposition, and found preformed in 

 every cartilage 1 and in the amyloid liver. 2 It is, of course, not a proteid. 



Nucleo-proteids, or Nucleo-albumins. 3 These are compounds of proteid with 

 nuclein, which latter yields phosphoric acid on decomposition. If nucleo-proteid, which 

 is found in every cell, be digested with pepsin-hydrochloric acid, there remains a residue 

 of insoluble nuclein, likewise insoluble in water but soluble in alkalies. If this nuclein 

 yields xanthin bases on further decomposition it is called true nuclein, if it fails to yield 

 these bases it is called paranuclein. 4 Nucleo-proteids yielding proteid and paranuclein on 

 decomposition include the casein of milk, pyin of the pleural cavity, vitellin of the egg, 

 Bunge's 5 iron-containing haematogen of the egg, as well as nucleo-proteids found in all 

 protoplasm. They all contain iron. Paranuclein is probably absorbable (see p. 958). 

 It is considered by Liebermann to be a combination of proteid and metaphosphoric acid 

 (see p. 958). 



A second group of nucleo-proteids yields true nuclein on decomposition. This group 

 includes the various nucleo-proteids which are constituents of different cell-nuclei. The 

 nuclein here obtained yields on decomposition nucleic acid, from which xanthin bases are 

 always to be derived. These xanthin bases vary in proportion and kind in the different 

 nucleic acids. Nucleic acid of yeast nuclein yields guanin and adenin, that of a bull's 

 testicle adenin, hypoxanthin, and xanthin, that of the thymus adenin alone. Kossel 6 

 calls this latter "adenylic acid," and speaks likewise of "guanylic," "xanthylic," etc., 

 acids, as provisional names for separate nucleic acids. Each one of this family of acids is 

 capable of combining with any soluble proteid to form nuclein, hence it is readily seen 

 that nucleins may exist in great variety. Another constituent of nucleic acid Kossel finds 

 to be thymin (a body derived from paranucleic acid, which latter, according to Kossel, is a 

 component of paranuclein). Some nucleic acids, such as those derived from yeast, pan- 

 creas, and the lactic glands, yield a reducing carbohydrate, while others (calf's thymus) 

 show the presence of the carbohydrate group only in the production of levulic acid after 

 very thorough decomposition, and still others (fish-sperm) fail to indicate any carbohydrate 

 radical as being present. A clearer idea of these relations is afforded by the following 

 schematic view of the decomposition of the nucleohiston, the constituent of blood-plates 

 and of the nuclei of leucocytes. 7 



1 Morner: Zeitschrift fur physiologische Chemie, 1895, Bd. 20, p. 357. 



2 Oddi: Archivfur exper. Pathologie und Pharmakologie, 1894, Bd. 33, p. 376. 



3 These two terms are used here as synonymous, though Hammarsten would confine the 

 term nucleo-albumin to those proteids which yield paranuclein. . It is difficult to give a definite 

 classification of these bodies, as the whole subject at present is in a transition stage. 



4 Kossel: Verhandlungen der Berliner physiologischen Gesellschaft, Archivjiir Physiologic, 

 1894, p. 194. 



6 Physiologische Chemie, 3d ed., 1894 p. 92. 5 Loc. cit. 



7 Lilienfeld : Zeitschrift fur physiologische Chemie, 1895, Bd. 20, p. 106. 



