5
This point, approximately, may be considered to be as follows
Per cent. NaC1.
Per cent. NaCl
Goat
0.706
Guinea pig
0.453
Sheep
o.67o
Dog
0.432
Horse
o.527
Man
0.418
Rabbit
0.514
Hen
0.365
Probably these differences do not depend so much on variations in the osmotic
pressure of the contents of the RBCs as on differences in the strengths of their
envelopes. This is rendered the more likely as the tonicities of the different
serums did not vary proportionately with the resistances of the RBCs.
(2) RBCs are lysed by acid and alkaline solutions of no great concentration,
-but very weak solutions of either have no lytic effect.
Nevertheless RBCs are altered by contact with very weak acids and alkalis
so that their resistance is raised by alkalis and lessened by acids. If RBCs
obmined by citration, are washed and divided into three portions, A for control, B for
-treatment with acid and C for treatment with alkali, this change can be readily
demonstrated.
A is allowed to rest at laboratory temperature ;
B is suspended in H Cl, 1 in 10,000, made up with NaC1 1 per cent. ;
C is suspended in Na2CO3, 1 in 3,300, made up with NaC1 1 per cent. ;
B & C are allowed to rest for 2 hours with occasional shakings and are then
centrifugated. The lytic points of A, B and C are then determined.
One such experiment with rabbit RBCs gave the following figures in per-
centages of NaCl.
A (Control). B (Treated with
acid).
C (Treated with
alkali.)
Trace lysis
.629
.799
.561
Per cent Na Cl.
Complete lysis
.493
.595
.357
Range
.136
.204
.204
Each tube contained 0.05 cc. RBCs to 2 .45 cc. of hypotonic salt solution.
It is clear that the action of the acid lessens the resistance and the action of
the alkali raises the resistance of RBCs to lysis by hypotonic solutions, i.e., the
acid renders the envelope of the RBC more readily permeable to water.
(3) It then seemed of interest to determine whether RBCs suspended in a
highly ionised solution such as 0.85 per cent. NaC1 (in this strength about 90 per
cent. of the salt is said to be ionised) are more under the influence of the negative
or of the positive ion. If the positive ion is the dominant one it would be ex-
pected that on its removal the resistance of the RBCs would be lowered ; if
the negative ion dominates, the RBCs freed from its influence would be able to
resist lysis better.
Three portions of rabbit RBCs obtained by citration and washing in o.85 per
cent. NaC1 were taken. A was suspended in 0.85 per cent. NaC1, B and C we're
washed in 8 per cent. cane sugar solution to remove the salt, and suspended in a
large bulk of 8 per cent. cane sugar and kept in the ice chest overnight to allow the
.minute quantity of NaC1 attached to the RBCs to diffuse away. In the morning
B and C were centrifugated and washed once in a fresh portion of sugar solution,
B was set aside and C was suspended in 1 per cent. NaC1 for 2½ hours.
The , resistances of A, B & C were then tested in hypotonic NaC1 solutions,
.with the result shown in the table.
A (Salt).
B (Sugar).
C (Sugar then salt).
Trace lysis
...
...
.578
.544
.578 Per cent. NaCl
Complete lysis ...
...
.442
.238
.306 ,.,
Range .,.
...
...
.136
.306
.272
Evidently the resistance of RBCs in a medium free from NaC1 is (greatly
increased and their susceptibility is restored by contact with NaCl, though not
completely within the time limit of this experiment.