THE GLUCO-PROTEIDS. 63 



By the action of dilute mineral acids on mucin, this reducing sub- 

 stance, whatever its exact nature is, is also obtained, together with syntonin 

 and proteose-like materials, from the proteid part of the mucin molecule. 

 Strong acids lead to the formation of leucine, tyrosine, and levulinic acid 

 (Landwehr). Strong alkalis lead to the formation of similar products ; 

 but weak alkalis, like lime water, have no effect on tendon mucin, though 

 they readily break up submaxillary mucin (Loebisch). There is a good 

 deal of difference among the mucins in their solubilities in acid and 

 alkaline solutions. Obolensky obtained pyrocatechin by boiling sub- 

 maxillary mucin with caustic soda ; but I have not succeeded in getting 

 it from connective tissue mucin. 1 



The putrefactive products of mucin are similar to those obtained 

 from proteids. 



Mucoids or mucinoids. These are mucin-like substances, which differ 

 from the true mucins either in being non-precipitable from alkaline solu- 

 tions by acetic acid, or in being readily soluble in excess of acetic acid. The 

 designation was originally given to this class by Hammarsten, and includes 

 the following substances : 



1 . The mucin from vitreous humour. 



2. The mucin from cartilage cliondro-inucoid (see " Cartilage "). 



3. The mucin from cornea cornea-mucoid. 2 



4. Pseudo-mucin ; the colloid-like substance often found in ovarian fluids, 

 and previously known as paralbumin and metalbumin. 3 



5. A similar mucoid, sometimes found in ascitic fluid. 4 



6. Ovomucoid, a mucoid found in white of egg. This was first studied 

 by Neumeister, 5 who called it pseudo-peptone, then by Salkowski, 6 and finally 

 by C. T. Morner, 7 who identified it as a mucoid. 



7. Paramucin, a substance found sometimes in ovarian cysts, differing 

 from pseudomucin in reducing Fehling's solution without previous treatment 

 with acids (K. Mitjukoff). 8 Leathes, 9 who has worked at this substance under 

 Drechsel's supervision, finds that the reducing substance yields no osazone ; 

 that on decomposition it yields sulphuric acid, and thus resembles chondro- 

 mucoid; and on treatment with hydrochloric acid it gives off carbonic anhydride. 

 Its nature is still uncertain. 



Hyaloyens. The term hyalin was originally applied to the principal 

 constituent of the wall of hydatid cysts. 10 Krukenberg 11 extended the 

 name to allied substances obtainable from other animal structures. In the 

 natural state these substances are insoluble, and are termed hyalogens; by the 

 action of alkalis or superheated water they are converted into the soluble 

 hyalins. Neossidin is the hyalin obtained from neossin, 12 the chief con- 

 stituent of the edible bird's nest. Chondrosidin and chondrosin are the hyalin 

 and hyalogen respectively obtained from the sponge, Gliondrosia reniformis, 



1 See also Young, loc. cit. 



2 C. T. Morner, Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 213. 



8 Hammarsten, "Lehrbuch d. physiol. Chem.," 3rd Gorman edition, S. 366. See also 

 Hammarsten, Jahresb. it. d. Fortschr. d. Thier-Chein. t Wiesbaden, Bd. xi. S. 11 ; Land- 

 wehr, Ztschr. f. physi ol. Chcvi., Strassburg, Bd. vii. S. 118. 



4 Hammarsten, ibid., 1891, Bd. xv. S. 202. 



5 Ztschr. f. Biol., Miinchen, Bd. xxvii. S. 309. 



6 CentralU.f. d. med. Wissensch., Berlin, 1893, Nos. 31 and 43. 



7 Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 525. 



8 Inaug. Diss., Berlin, 1895. 



9 Communication to Physiological Society, London, Oct. 17, 1896 (not published). 



10 Lilcke, Virchow's Archiv, Bd. xix. S. 189. 



11 Ztschr. f. BioL, Miinchen, Bd. xxii. S. 261. 



1:2 The word "neossin" is Mulder's, Butt, des sc. phys. in Ncdwlandc, 1838, S. 172; 

 Green, Journ. Physiol., Cambridge and London, vol. vi. p. 40, pointed out the resemblance 

 of the nest substance to mucin. 



