14 PROTEIDS. 



that diffused in the tissues ; in chyle, milk, transudations, and 

 many pathological fluids. 



It is this form in which albumin generally appears in the urine. 



Scherer described' two proteids which he obtained from the contents 

 of ovarial cysts, and to which he gave the names of metalbuinin and 

 paralbumin. 1 Hammarsten concludes from his researches 2 that they 

 are really identical. Metalbumin seems to be associated with some 

 carbohydrate substance resembling glycogen (?), since it yields, on 

 heating with sulphuric acid, a body which reduces Fehling's fluid as 

 does dextrose. 8 



Neither egg- nor serum-albumin can be obtained in a condition such 

 that They leave no ash residue on ignition. Al. Schmidt asserted * 

 that they could be by means of dialysis, and that in this condition 

 they were no longer coagulable by heat. On this point a keen con- 

 troversy was carried on for some time, for the details of which see 

 Rollett's article on Blood in Hermann's Hdbch. d. Physiol. Bd. iv. 

 Th. 1, S. 93. The whole difficulty seems to have turned on the ex- 

 treme sensitiveness of dialysed solutions of albumin to the presence 

 or absence of traces of acid or alkali, and on the fact that such dialysed 

 albumin is largely changed into an albuminate. 6 



Preparations of pure serum-albumin. Centrifugalised serum is 

 saturated at 30 with magnesium sulphate, and the precipitated 

 globulin 6 is washed on the filter with a saturated solution of the 

 salt. The filtrates are then saturated at 40 with sodium sul- 

 phate; by this means the serum-albumin is precipitated. The 

 precipitate is dissolved in water, reprecipitated by sodium sul- 

 phate, and the process repeated several times. The final product 

 is then freed from salts by dialysis, precipitated by excess of 

 alcohol, washed with this, and finally with ether, and dried by 

 exposure to the air." 



The facts on which this method is based were clearly stated by 

 Denis. 8 Schafer rediscovered 9 the precipitability of serum-albumin 

 by sodium sulphate in presence of the magnesium salt. Halliburton 

 has shewn 10 that this is due to the action of the double sulphate of 

 magnesium and sodium MgNa 2 (S0 4 ) 2 6 H 2 0. 



1 Ann. d. Chetn. u. Pharm. Bd. 82 (1852), S. 135. 



2 Maly's Bur. Bd. xi. (1881), S. 11. Zt. physio/. Ch. Bd. vi. (1882), S. 194. 



3 Landwehr, Pfliiger's Arch. Bd. xxxix. (1886), S. 203. Zt. physiol Chem. Bd. 

 vui. (1883), S. 114. Hilger, Annal. d. Chem. Bd. 160 (1871), S. 338. Plo'sz, Hoppe- 

 Seyler's Med.-Chem. Unters, (1871), S. 517. Obolensky, Pfliiger's Arch. Bd. iv. 

 (1871), S. 346. 



* Pfliiger's Arch. xi. (1875), S. 1. 



5 Werigo, Pfliiger's Arch. Bd. XLVIII. (1890), S. 127. 



6 Hammarsten, Zt. f. physiol. Ch. Bd. vui. (1884), S. 467. 



7 Starke, loc. cit. (sub. egg-albumin), S. 18. 



8 Etudes sur le sang, Paris, 1859, p. 39. 



9 Jl. of Physiol. Vol. in. (1880), p. 184. 

 10 Ibid. Vol. v. 1883, p. 181. 



