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RETICUUN. 121
Diethyl alcohol, and partly insoluble 1 herein. The peptones obtained from
these salts contain less carbon and more hydrogen than the gelatin from which
they originated, showing that hydration has taken place. The molecular weight
of the gelatin peptone as determined by PaAL, by RaOULT’s cryoseopic method,
was 200 to 352, while that for gelatin was 878 to 960. The gelatin peptones
isolated by Siegfried and his pupils which will be discussed below, are of great
interest.
Collagen (contaminated with mucoid) may be obtained from bones by
extracting them with hydrochloric acid (which dissolves the earthy
phosphates) and then carefully washing the acid out with water. It
may be obtained from tendons by extracting with lime-water or dilute
alkali (which dissolve the proteids and mucin), and then thoroughly
washing with water. Gelatin is obtained by boiling collagen with water.
The finest commercial gelatin always contains a little proteid, which
may be removed by allowing the finely divided gelatin to swell up in
water and thoroughly extracting with large quantities of fresh water.
Then dissolve in warm water and precipitate with alcohol.
Collagen may also be purified from proteids, as suggested by van
Name, by digesting with an alkaline trypsin solution or by extracting
the gelatin for many days with 1-5 p. m. caustic potash, as suggested
by C. Morner. The typical properties of gelatin are not changed by
this.
Chondrin or cartilage gelatin is only a mixture of gelatin with the specific
constituents of the cartilage and their transformation products.
Reticulin. The reticular tissues of the lymphatic glands contain a
variety of fibers which have also been found, by Mall in the spleen, intes-
tinal mucosa, liver, kidneys, and lungs. These fibers consist of a special
substance, reticulin, investigated by Siegfried.1
Reticulin has the following composition: C 52.88; H 6.97; N 15.63;
S 1.88; P 0.34; ash 2.27 per cent. The phosphorus occurs in organic
combination. It yields no tyrosine on cleavage with hydrochloric acid.
It yields, on the contrary, sulphureted hydrogen, ammonia, lysine,
arginine, and valine. On continued boiling with water, or more readily
with dilute alkalies, reticulin is converted into a body which is precipitated
by acetic acid, and at the same time phosphorus is split off.
Reticulin is insoluble in water, alcohol, ether, lime-water, sodium
carbonate, and dilute mineral acids. It is dissolved, after several weeks,
on standing with caustic soda at the ordinary temperature. Pepsin-
hydrochloric acid or trypsin does not dissolve it. Reticulin responds
to the biuret, xanthoproteic, and Adamkiewicz-Hopkins reactions,
but not to Millon’s reagent.
1
Mall, Abhandl. d. math.-phys. Klasse d. Kgl. sachs. Gesellsch. d. Wiss., 1891;
Siegfried, Ueber die chem. Eigensch. der retikulirten Gewebe, Habil.-Schrift, Leipzig,
1892.
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