In English parliamentary law. Forty members form a house of commons; and, though there be ever so many at the beginning of a debate, yet, if during the course of it the house should be deserted by the members, till reduced below the number of forty, any one member may have it adjourned upon its being counted; but a debate may be continued when only one member is left in the house, provided no one choose to move an adjournment Wharton.
Black’s Law Online Dictionary
