RELATIVE AMOUNT OF PLASMA AND CORPUSCLES. 147 



by allowing the blood as it flows from a cut artery to mix with an equal 

 volume of saturated solution of sulphate of soda or with a 10 per cent, 

 solution of sodium chloride, or with one-third its bulk of a saturated 

 solution of sulphate of magnesia. The plasma obtained after subsidence 

 of the corpuscles is in these cases diluted with the salt solution (salted 

 plasma), and may remain indefinitely uncoagulated. But, on diluting it 

 with a sufficient amount of water, coagulation will usually occur. The 

 delay produced by albumoses (commercial " peptone " is generally used) 

 is obtained by injecting these, in the proportion of 0'3 grm. per kilog. of 

 body weight into the circulating blood of a dog or cat. 1 The effect is 

 not got in the rabbit. 2 Malt diastase and emulsin in somewhat larger 

 quantity have a similar effect. 3 The blood of such a " peptonised " 

 animal does not clot on being drawn, but it coagulates on passing 

 carbonic anhydride through it, or on diluting it with water. Extract of 

 leech-heads, 4 which contains an albumose, 5 and also extract of crayfish 

 muscle (Heidenhain), act similarly in preventing coagulation, but in smaller 

 doses. Leech extract does not, however, act exactly in the same manner as 

 albumose, for the latter does not arrest coagulation if added in moderate 

 quantity to drawn blood, whereas leech extract does arrest it (Haycraft). 



To hinder coagulation by removal of lime salts, the blood is mixed as it 

 flows from the vessels with a small amount of solution of sodium oxalate ; 

 1 part of the salt to 1000 parts of blood is sufficient. 6 The corpuscles 

 usually subside very readily in oxalated blood, and a clear plasma, nearly 

 but not quite free from soluble lime salts, is easily got from it, coagulating 

 quickly on the addition of chloride of calcium. It is not, however, the 

 case that, as Arthus has asserted, oxalated blood or plasma always 

 remains indefinitely uncoagulated without the addition of lime salts, 

 for on allowing it to stand a few days a clot is frequently found in it. 7 



All the above methods yield plasma, either pure or in a somewhat 

 modified condition. To obtain the blood corpuscles free from plasma it 

 is necessary, after drawing off the superjacent fluid from them, to mix 

 them with a further quantity of the salt solution used to prevent 

 coagulation (e.g. 10 per cent. NaCl), and again to centrifugalise. Or 

 the blood may be mixed as soon as drawn with a sufficient quantity of 

 isotonic salt solution to delay its coagulation, and centrifugalised. By 

 repeating the process several times the corpuscles may be got free from 

 plasma, and may thus be analysed separately from the liquor sanguinis. 

 But it is by no means certain that they have not undergone some altera- 

 tion in composition by diffusion. Hitherto no means has been devised 

 for meeting this objection. 



Relative amount of plasma and corpuscles. The relative amounts 

 of plasma or serum and corpuscles can therefore only be found approxi- 

 mately by weighing the corpuscles obtained by this method from a 

 given amount of blood. Indirectly, it has been arrived at for defibrin- 

 ated blood by Hoppe-Seyler, by determining the percentage amount of 



1 Schmidt-Mulheim, Arch. f. PhysioL, Leipzig, 1880, S. 33. 

 2 Fano, ibid., 1881, S. 276. 



3 Salvioli, Arch, per le sc. med., Torino, 1888, vol. xii. p. 245. 



4 Haycraft, Proc. Roy. Soc. London, 1884, vol. xxxvi. p. 478. Haycraft showed that luech 

 extract acts by destroying fibrin ferment. 



5 Dickinson, Journ. PhysioL, Cambridge and London, 1890, vol. xi. p. 566. 



6 Arthus et Pages, Arch, dephysiol. norm, etpath., Paris, 1890, p. 739. 



7 This is certainly so with the plasma obtained from oxalated dog's blood and sheep's 

 blood (Schafer, Proc. PhysioL Soc., Journ. PhysioL, Cambridge and London, 1895, vol. 

 xvii. p. xx). 



