(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.
A compound verb is usually composed of a preposition and a verb, although other combinations also exist. The term compound verb was first used in publication in Grattan and Gurrey's Our Living Language (1925). From a morphological point of view, some compound verbs are difficult to analyze because several derivations are plausible. Blacklist, for instance, might be analyzed as an adjective+verb compound, or as an adjective+noun compound that becomes a verb through zero derivation.