RETICULIN. 121 



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methyl alcohol, and partly insoluble therein. 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 cryoscopic method, 

 was 200 to 352, while that for gelatin was 878 to 950. 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. 



