THE GLUCO-PROTEIDS. 63 
By the actioD of dilute mineral acids on mucin, this reducing sub- 
stance, whatever its exact nature is, is also obtained, togetherwith syntonin 
and proteose-like materials, from the proteid pari of the mucin molecule. 
Strong acids lead to the formation of leucine, tyrosine, and levulinie acid 
(Landwehr). Strong alkalis lead to the formation of similar products ; 
luit 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 1 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 mucinlike 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 — chondro-mucoid (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 fust studied 
by Xeumeister, ' 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, 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. 
Hyalogens. — 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, Cliondrosia reniformis, 
1 See also Young, loc. cit. 
2 0. T. Morner, Ztschr.f. pkysiol Chem., Strassburg, Bd. xviii. S. 213. 
3 Hammarsten, "Lehrbuch d. physiol. Chem.," 3rd German edition, S. 366. See also 
Hammarsten, Jahrcsb. it. d. Fortschr. <K Thier-Ghein., Wiesbaden, Bd. xi. S. 11; Land- 
wehr. Ztschr. f. physiol. ''fin,/., Strassburg, Bd. vii. S. 118. 
I Hammarsten, ibid., 1891, Bd. xv. S. 202. 
5 Ztschr.f. Biol., Munchen, Bd. xxvii. S. 309. 
II Cenlralbl.f. d. med. Wissensch., Berlin, 1893, Nos. 31 and 43. 
7 Ztschr.f. physiol. Chew,., Strassburg, Bd. xviii. S. 525. 
8 Inaug. Diss., Berlin, 1895. 
9 Communication to Physiological Society, London, Oct. 17, 1896 (not published). 
1J Lucke, Virchov's A rchiv, Bd. xix. S. 189. 
11 Ztschr.f. Biol., Munchen, Bd. xxii. S. 201. 
12 The word "neossin" is Mulder's, Bull, des sc. phys. in Kedcrlande, 1838, S. 172; 
Green, Journ. Physiol., Cambridge and London, vol. vi. p. 40, pointed out the resemblance 
of the nest substance to mucin. 
