TUEGIDITY 57 



coefficients hold true only within certain limits, and since 

 other more accurate methods are now available for deter- 

 mining the amount of ionization, a discussion of them is 

 here omitted.' 



On the animal side the method of plasmolysis has been 

 used by Hamburger and others ' for determining the osmotic 

 pressures of the fluid contained in blood corpuscles. 



Another method for comparing the osmotic pressure of 

 the fluid contained in red blood corpuscles with that of 

 the surrounding fluid was devised by KOppe,' and further 

 used by Lob* and Hedin.* The total volume of all the cor- 

 puscles of a given amount of blood was first determined by 

 separating them from the plasma by means of the centrifuge. 

 Then a known amount of blood was added to a given volume 

 of salt solution of known concentration, and the mixture was 

 shaken thoroughly. The corpuscles were then separated 

 from the solution on the centrifuge, and their total volume 

 carefully measured. If the resulting volume was less than 

 the normal for the given amount of blood, the conclusion 



1 It will be well for physiology when the practical use of these coefficients dies 

 out entirely. 



2 H. J. Haubusgeb, " Ueber den Einflnss chemisoher Verbindungen anf Blut- 

 kOrperchen in Zusammenhang mit ihren Molekulargewichten," Arch. f. Anat. u, 

 Physiol., Physiol. Abth., Jahrg. 1886, pp. 476-87; edem, " Ueber die dnrch Salz- nnd 

 EohrzuckerlOsungen bewirkten Verandeningen der BlutkOrperchen," ibid., Jahrg. 

 1887, pp. 31-47; IDEM, "Die Permeabilitftt der rothen BlutkOrperchen in Zusammen- 

 hang mit den isotonischen Coefficienten," Zeitschr. f. Biol., Vol. XXVI (1889), pp. 

 414^33; G. Geyns, "Ueber d. Einflnss gelOster Stoffe auf d. rothen Blutzellen, in Ver- 

 bindung mit d. Erscheinungen der Osmose u. Diffusion," Pfiilgers Arch. f. d. ges. 

 Physiol., Vol. LXIII (1896), pp. 86-119; H. KOppe, "Physiologische KochsalzlOsung— 

 Isotonic— osmotischer Druck," ibid., Vol. LXV (1897), pp. 492-502. 



3H. KOPPE, "Eine neue Methode zur Bestimmung isotonischer Eonzentrati- 

 onen," Zeitschr. f. physik. Chem., Vol. XVI (1895), pp. 261-88. 



* W. LOb, "Ueber Molekulargewichtsbestimmnng von in Wasser lOslichen Sub- 

 Btanzen mittels der rothen BlutkOrperchen," ibid.. Vol. XTV (1894), pp. 424-32. 



5 S. G. Hedin, "Ueber d. Brauchbarkeit der Centrifugalkraf t fttr quantitative 

 Blutuntersuchungen," Pftilgers Arch. f. d. ges. Physiol., Vol. LX (1895), pp. 360- 

 404; IDEM, "Ueber d. Bestimmung isotonischer Konzentrationen durch Zentrifugieren 

 von Blutmischnngen," ZeiUchr.f. physik. Chem.., Vol. XVII (1895), pp. 164^-70; IDEM, 

 " Einige Bemerkungen KOppes Abhandlung : Ueber eine neue Methode, etc.," ibid., 

 Vol. XXI (1896), pp. 272-6. 



