(February 2013) Durham tubes are used in microbiology to detect production of gas by microorganisms. They are simply smaller test tubes inserted upside down in another test tube. This small tube is initially filled with the solution in which the microorganism is to be grown.
A compound predicate is two or more simple predicates joined by a conjunction that indicate actions by the same subject. Example : Bill picked up the mail and walked the dog.. Bill is the subject for both verbs.
Defining a Predicate. Simply put, the predicate of a sentence is the part that modifies the subject in some way. Because the subject is the person, place, or thing that a sentence is about, the predicate must contain a verb explaining what the subject does.