The living bivalves have the 3 forces concerning to close the valves: namely the closing force of adductor muscle, the opening force of ligament of valves and the adhesive force of adductor muscle to the shells.
The closing force of adductor muscle decreases gradually as temperature rises and becomes minimum at about 70°C and increases as temperature rises higher until the shell opens. The force of ligament increases by degrees as temperature rises so as to open the valves. The adhesive force of adductor muscle to the shell is exceedingly strong in lower temperatures but it decreases as temperature rises so far as the shell opens. The sementing substance between the adductor muscle and the shell dissolves at length completely by prolonged boiling.
The results of my observations and experiments show that when the closing force of adductor muscle or the opening force of ligament exceeds the adhesive force of adductor muscle to the shell the adductor muscle comes off from one side of the valves, which open widely at last.
