1. the governing or limitation of certain objects or events.
2. a standard against which experimental observations may be evaluated, as a procedure identical to the experimental procedure except for the one factor being studied; a requirement of any planned experimental study. Also, any individual of the group exhibiting the standard characteristics.
- disease c. — restraining or reducing the prevalence of individual disease. Includes the range of strategies from limitation of occurrence to eradication. Implies legislative control of notifiable disease.
- c. elements — nucleotide sequences on DNA that usually precede (upstream) the sequences coding for the structural gene at which regulator proteins act.
- c. factor — in a comparison between diseases caused by a number of contributing factors it may be necessary to supply controls for one or more of these factors.
- c. group — the group of animals with which the experimental group is to be matched; the group which has not had its variables manipulated experimentally. The selection of the animals to be included in the two groups may be based on matching them with respect to age, to their history of nutrition or inheritance, or vaccination or prophylactic treatment. Called also controls.
- ovulation c. — prevention of ovulation by administration of progesterone or stimulation of ovulation by injection of follicle-stimulating hormone are examples.
- paired c. — comparison between the experimental and control groups is most accurate if the control animal for each experimental animal is selected to be as similar as possible, i.e. a paired control.
- c. pole — a pole with a noose at the end used to catch and restrain small animals.
- c. population — a large control group.
- population c. — a variety of techniques are used with contraception being least used. Permanent surgical interference is common in food, racing and companion animal groups, and termination of pregnancy and estrus synchronization, both by hormonal means, are also extensively practiced. Increasing the culling rate is the standard procedure for dealing with a feed shortage.
- x-ray c. unit — the controlling mechanisms in an x-ray machine. Include the voltmeter and voltage compensator control, the kilovoltage, milliameter and milliamperage selectors and the timer and exposure control button.
