Webster's New World Medical Dictionary

lateral meniscus of the knee
A thickened cres-
cent-shaped cartilage pad in the outer portion of the
joint formed by the femur (thigh bone) and the tibia
(shin bone). The lateral meniscus acts as a smooth
surface for the joint to move on. The lateral menis-
cus is toward the outer side of the knee joint. It
serves to evenly load the surface during weight-
bearing, and also aids in disbursing joint fluid for
joint lubrication. See also 
knee.
lateral ventricle
A communicating cavity in the
brain that is part of a system of four communicating
cavities that are continuous with the central canal of
the spinal cord. The two lateral ventricles are located
in the cerebral hemispheres, one in each hemi-
sphere. Each consists of a triangular central body
and four horns. The third and fourth ventricles are
located in the center of the brain. The lateral ventri-
cles communicate with the third ventricle through an
opening called the interventricular foramen. Both
lateral ventricles are filled with cerebrospinal fluid.
lateral X-ray
An X-ray taken from the side of the
patient.
latex allergy
An allergic reaction to the protein
found in rubber latex. Latex is made from a natural
product of tropical rubber trees and is found in sur-
gical gloves, balloons, condoms, rubber bands,
pacifiers, and many other products. The allergic
reaction can be mild, consisting of bumps or a rash
on the skin in areas of contact with latex, or severe
enough to cause life-threatening complications.
laughing gas
See 
nitrous oxide.
lavage
Washing out. Gastric lavage, for example,
is the washing out of the stomach to remove drugs
or poisons.
law, Hardy-Weinberg
See 
Hardy-Weinberg law.
laxative
Something that promotes emptying of
the bowels. Laxatives are used to combat constipa-
tion. They are sometimes overused, producing diar-
rhea. Laxatives include milk of magnesia and many
others.