r.i' PROTEIDS. 



been prepared in sufficient quantity l to admit of the easy and 

 decisive application of the modern methods of organic chemistry 

 to the elucidation of their molecular structure. Work in this 

 direction on a really large scale could scarcely fail to yield im- 

 portant results. Schrotter 2 has recently described the preparation 

 of benzoylated ethers of the albumoses, and intends to apply the 

 method to other proteids and to study the products of decom- 

 position and oxidation of these substances. Whether any real 

 advance will be made in this direction cannot be foretold, but 

 this new departure is of considerable prospective importance. 



No account of the constitution of proteids would be complete 

 without a reference to the views and theories of Pfliiger, and of 

 Low and Bokorny. Pfliiger 3 starting from the characteristic dif- 

 ferences between the products obtained by decomposing dead pro- 

 teids by chemical means out of the body, and the products which 

 arise by the natural decomposition (metabolism) of living proteids 

 (protoplasm) in the body, has put forward a view as to the dif- 

 ference of living and dead proteid. He considers that in dead 

 proteid the nitrogen exists in the amide foun. while in living 

 proteid it is present in the less stable cyanic form. The build- 

 ing-up of living proteid from dead he regards as being carried on 

 by the ether-like union of the isomeric living and dead proteid 

 molecules, accompanied by the 'elimination of water. During this 

 process the nitrogen of the dead proteid passes into the cyanic 

 condition, and if this is repeated and accompanied by polymerisa- 

 tion the formation of a large and unstable living proteid molecule 

 may be readily accounted for. He further draws attention to the 

 readiness with which polymerisation occurs in the cyanic series 

 and the extraordinarily high molecular energy of cyanogen. Low 

 and Bokorny 4 deal also with the probable mode by which, in the 

 case at least of plant cells, the complex proteid molecule may be 

 built up out of the simpler substances from which these obtain 

 their nitrogen. They consider there is evidence of the existence 

 in living plant cells of some substance of an aldehyde nature. 

 Starting with formic aldehyde, by its union with ammonia the 

 aldehyde of aspartic acid might be obtained, and by polymerisa- 

 tion of the latter in presence of sulphur and with the exit of 

 water a substance with the same composition as an ordinary proteid 

 would arise. Their speculations are ingenious, but it cannot by 

 any means be said that their views are established. Asparagin, 

 from which aspartic acid is readily obtained, undoubtedly plays 

 an all-important part in the constructive nitrogenous metabol- 



1 But see Chittenden and Hartwell JL of Physiol. Vol. xi. (1890), p. 435. 



2 Ber. d. deutsch. chem. Gesell. Jahrg. xxn. (1889), S. 1950. 



3 Pfliiger's Arch. Bd. x. (1875), S. 332. 



4 Low and Bokorny's work may be most conveniently quoted by reference to the 

 following volumes of Maly's Jahresbe.richt d. Tkierchem'. Bde. x. (1880), S. 3 ; xi. 391 , 

 394; xn. 380; xm. 1; xiv. 349, 474; xvi. 8; xvn. (1887), 395. See also Bid. 

 Centralb. Bd. I. (1881), S. 193; vin. (1888), S. 1. 



