542 ANIMAL PHYSIOLOGY. 
columns of the cord, while upward these fibers connect with 
the crura cerebri and so with the cortex. 
Pathological—__Paralysis of the face usually occurs on the 
same side as that of the rest of the body; hence it must be 
inferred that there is a decussation somewhere of the fibers of 
the facial nerve; but there is much still to be learned about this 
subject. 
Medulla Oblongata.—In some animals (frogs) it is certainly 
known that this region of the brain has a co-ordinating func- 
tion, and it is probable that it is concerned with such uses in 
all animals that possess the organ, or rather collection of organs, 
seeing that this part of the brain must be regarded as especially 
a mass of centers, the functions of which have been already 
considered at length. So long as the medulla is intact, life may 
continue; but, except under special circumstances, which do 
not invalidate this general statement, its destruction is followed 
by the death of the animal. 
We may simply enumerate the centers that are usually 
located in the medulla: The respiratory (and convulsive), car- 
dio-inhibitory, vaso-motor, center for deglutition, center for 
the movements of the gullet, stomach, etc., and the vomiting 
center; center for the secretion of saliva and possibly other of 
the digestive fluids. Some add a diabetic and other centers. 
SPECIAL CONSIDERATIONS. 
Embryological_—The further we progress in the study of the 
nervous system, the greater the significance of the facts of its 
early development becomes. It will be remembered that from 
that uppermost epiblastic layer of cells so early marked: off in 
the blastoderm, is formed the entire nervous system, including 
centers, nerves, and end organs. The brain may be regarded 
Fic. 391.—Vertical longitudinal section of brain of human embryo of fourteen weeks. 1 x 3. 
(After Sharpey and Reichert.) c, cerebral hemisphere ; cc, corpus callosum beginning to 
ass back ; f, foramen of Munro; P. membrane over third ventricle and the pineal body ; 
h. thalamus ; 3, third ventricle ; I, olfactory bulb ; cg, corpora quadrigemina ; cr, crura 
cerebri, and above them, aqueduct of Sylvius, still wide ; c’, cerebellum, and below it the 
