junction with the supra and infraorbital canals behind
themid-eye, and extending back to the rear of the head
connecting to the lateral line.
lateral meristem An embryonic tissue, the meristem,
on the portion of a plant that gives rise to secondary
growth such as the cambium, vascular cambium, and
cork cambium. Runs most of the length of stems and
roots. Also called the cambium.
Laurasia Laurasia was the northern supercontinent
formed after PANGAEAbroke up during the JURASSIC
PERIOD some 180 million years ago and formed
the present continents of North America, Europe, and
Asia as well as the land masses of Greenland and
Iceland.
lava Igneous rock, magma that exits volcanoes and
vents and reaches the exterior or surface of the land or
seabed.
Laveran, Charles-Louis-Alphonse (1845–1922) French
Physician, Protozoologist Charles-Louis-Alphonse Lav-
eran was born in Paris on June 18, 1845, in the house
at 19 rue de l’Est, to Dr. Louis Théodore Laveran, an
army doctor and professor at the École de Val-
de-Grâce, and Guénard de la Tour, the daughter and
granddaughter of high-ranking army commanders.
After completing his education in Paris at the
Collège Saint Baube and later at the Lycée Louis-
le-Grand, he applied to the Public Health School at
Strasbourg in 1863 and attended the school for four
years. In 1866 he was appointed a resident medical
student in the Strasbourg civil hospitals, and the fol-
lowing year he submitted a thesis on the regeneration
of nerves. In 1874 he was appointed to the chair of
military diseases and epidemics at the École de Val-
de-Grâce, previously occupied by his father, and in
1878, when his period of office had ended, he moved
to Bône in Algeria until 1883. It was during this peri-
od that he carried out his chief researches on the
human malarial parasites, first at Bône and later at
Constantine.
In 1880 Laveran examined blood samples from
malarial patients and discovered amoebalike organisms
growing within red blood cells, and he noticed that
they divided, formed spores, and invaded unaffected
blood cells. He also noted that the spores were released
in each affected red cell at the same time and corre-
sponded with a fresh attack of fever in the patient. His
researches confirmed that the blood parasites that he
had described were in fact the cause of malaria, but his
first publications on the malaria parasites were received
with skepticism until scientists around the world pub-
lished confirmative research results. In 1889 the Acade-
my of Sciences awarded him the Bréant Prize for his
discovery.
In 1896 he entered the Pasteur Institute as chief of
the Honorary Service, and from 1897 until 1907 he
carried out many original research projects on
endoglobular haematozoa and on sporozoa and try-
panosomes. In 1907 he was awarded the Nobel Prize
for his work on protozoa in causing diseases. In 1908
he founded the Société de Pathologie Exotique, over
which he presided for 12 years.
He was the first to express the view that the malar-
ial parasite must be a parasite of Culicidae,and after
this view had been proved by the research of Ronald
Ross, he played a large partin the enquiry on the rela-
tionships between Anophelesand malaria in the cam-
paign undertaken against endemic disease in swamps,
notably in Corsica and Algeria.
From 1900 on, he studied the trypanosomes and
published, either independently or in collaboration
with others, a large number of papers on these blood
parasites. His research concentrated on the try-
panosomes of the rat; the trypanosomes that cause
nagana and surra; the trypanosome of horses in Gam-
bia; a trypanosome of cattle in the Transvaal; the try-
panosomiases of the Upper Niger; the trypanosomes of
birds, chelonians, batrachians, and fishes; and finally
the trypanosome that causes the endemic disease of
equatorial Africa known as sleeping sickness. For 27
years he worked on pathogenic protozoa and the field
heopened up by his discovery of the malarial parasites.
He died on May 18, 1922.law of equal segregation Gregor Mendel’s first law,
which says that two copies of a gene separate duringlaw of equal segregation 197