RELATIVE AMOUNT OF PLASMA AND CORPUSCLES. 147 
by allowing the blood as it flows from a cul artery to mix with an equal 
volume of saturated solution of sulphate of soda or with a 10 percent, 
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 Ball 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 Mood 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 hi I 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 allmmose, 5 and also extract of crayfish 
niiiscle(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 a- 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 nece»arv, 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 1 if 
1 Schmidt-Miilheim, Arch. f. Physiol., Leipzig, 18S0, S. 33. 
- Fano, ibid., 1881, S. 276. 
3 Salvioli, Arch. ^ r h sc. rued., Torino, 1888, vol. xii. p. 245. 
4 Haycraft, Proc. Pot/. Soc. London, 1884, vol. xxxvi. p. 478. Haycraft showed that leech 
extract acts by destroying fibrin ferment. 
5 Dickinson, Journ. Physiol., Cambridge and London, 1890, vol. xi. p. 566. 
,; Arthus et Pages, Arch, dephysiol. norm, etpaih., 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). 
