Slowing down lysis

Experiment 2: Effect of hypotonic saline (50% saline)

Because biological systems are stochastic not deterministic, there will be variation from trial to trial in the responses elicited from a system, for a variety of reasons. Hence, it is important to repeat the same test a number of times to obtain the mean response of the system and determine reproducibility.

NOTE: This model assumes that the system is invariant from trial to trial and this is, as is clear for many biological systems, often not a good assumption to make.


  1. Add 2.5mL of each solution into the test tube to make 5mL of 50% Physiological saline.
  2. Now add a couple of drops of blood into the test tube.
  3. A timer will start automatically. Stop the timer when the solution inside the tube becomes clear enough to see the lightbulb filament.
  4. Record how long it takes for lysis to occur in the table below. Repeat the experiment two more times to calculate the average.
Trial 1 Trial 2 Trial 3 Mean
Haemolysis time