438 THE FORMS OF CELLS [ch. 



Whatever the forces are which make and keep the man's corpuscle 

 a dimpled disc and the frog's a flattened ellipsoid, they seem to be 

 of a powerful kind. When we submit either to great hydrostatic 

 pressure, it tends to become spherical at last, the natural result of 

 uniform pressure over its whole surface; but the pressure necessary 

 to bring this result about is very great indeed*. Since the form 

 of the blood-corpuscle cannot, then, be rated as a figure of equili- 

 brium, we must be content to regard it as a "steady state"; and 

 this, moreover, is all we can say of its physico-chemical conditional 

 The red blood-corpuscle, especially the non-nucleated one, is in no 

 ordinary sense alive'f. It has no power of movement, of reproduction 

 or of repair; it is a mere haemoglobin-freighted drop of protein; 

 its own metabolism, apart from its alternate give and take of 

 oxygen, is slight indeed or absent altogether. But all the same, 

 chemical change is continually going on; anions (Uke HCO3) pass 

 freely through its walls, simple cations (like Na, K) find it imper- 

 meable; and so, between plasma and corpuscles the conditions are 

 fulfilled for that steady osmotic state known as a "Donnan equi- 

 Kbrium." Somehow, but we know not how, a steady state is 

 maintained alike in the corpuscle's osmotic equihbrium and in its 

 form. 



In mammalian blood, the running together of the round biconcave 

 corpuscles into "rouleaux" gives a well-known and characteristic 

 picture. When cold, rouleaux are formed slowly, in warmed plasma 

 they form quickly and well, in salt-solution they do not form at all. 



* The whole phenomenon would become simple and mechanical if we might 

 postulate a stiffer peripheral region to the corpuscle, in the form (for instance) of an 

 elastic ring. Such an annular stiffening, like the " collapse-rings" which an engineer 

 inserts in a boiler or the whalebone ring which a Breton fisherman fits into his beret, 

 has been repeatedly asserted to exist; by Dehler, Arch.f. mikr. Anat. xlvi, 1895; by 

 Meves, ibid. Lxxvii, 1911; and especially by J. Riinnstrom, Was bedingt die Form 

 und die Formveranderungen derSaiigetiererythrocytcn, Arch. f. Entw. Mech. i, pp. 

 391-409^,1922. It has been denied at least as often; but the remarkable statement 

 has been lately made that in a corpuscle which has been swollen up and then brought 

 back to its biconcave form, the dimples reappear on the same sides as before: 

 apparently in "strong evidence for some sort of fixed cellular structure"; see 

 R. F. Furchgott and Eric Ponder in Jonrn. Exp. Biol. xvii. pp. 30-44, 117-127, 

 1940. See also, on the whole subject, Eric Ponder, The Mammalian Red Cell, 

 Berlin, 1934. 



t Cf. A. V. Hill, Trans. Faraday Soc. xxvi, p. 667, 1930; Proc. R.S. (B), 1930; 

 K. R. Dixon, in Current Sci. vii, p. 169, 1938; etc. 



