GLOSSARY 451 



pterygoid. A portion of the mandibular arch which doubtfully becomes the pterygoid 



process of the mammalian sphenoid. 

 ptyalin. The starch-splitting enzyme found in tlie saliva. 

 puberty. The age at which reproductive organs start to function, 

 pubis. The anterior of the two ventral arms of the peMc girdle. 

 Purkinje cells. Large much-branched neurons of the cerebellar cortex. 

 putamen. The outer darker portion of the lenticular nucleus of the corpus striatum. 

 pylorus. The aperture at the posterior end of the stomach. 

 pyramids, renal. The conical masses present in the medulla of the kidney. 

 pyramids of the medulla. Paired eminences on the ventral side of the medulla. 

 pyramidal cells. Neurons with pyramid-shaped cell-bodies in the cerebral corle.x. 



Rathke's pouch. The hypophysis of amniote embrj'os. 



ray-finned fishes. Fishes with bony and horny rays — includes most fishes. 



recapitulation theory. The theory that individual development repeats briefly the 



evolutionary history of the race. 

 receptaculum (cisterna) chyli. A chamber for the storage of lymph at the lower end 



of the thoracic duct. 

 receptor. A sensory cell. 



rectiun. The lower six to eight inches of the large intestine. 

 red nucleus. A nervous center in the tegmentum of the midbrain. Its cells contain 



a red pigment. 

 reduction. Meiosis. The process by which the hapluid number of chromosomes is 



attained. 

 reflex action. An action which involves a reflex arc, i.e., a sensory and a motor neuron 



connected within a central nervous system. 

 renal corpuscle. The expanded termination of an excretory tubule containing a 



glomerulus. 

 respiration. The regulated burning of carbon compounds within living cells. 

 restiform bodies (inferior peduncles). A fiber tract which connects sensory spinal 



nerves with the cerebellum. 

 rete testis. A network of fine ductules between the seminiferous tubules and the 



ductuli efferentes. 

 retina. The sensory innermost layer of the eye. 

 Rhodesian man. A prehistoric type of man having affinities with the Neanderthal 



man. 

 "rhomboid." A kite-shaped area where four hair currents meet. 

 rhombomere. A hindbrain neuromere. 



roof plate. The median dorsal wall of the embryonic neural tube. 

 rods and cones. The receptor cells of the retina. 

 rubrospinal tract. A longitudinal fiber tract which connects the red nucleus with the 



somatic motor cells of the spinal cord. 

 nunen. The anteriormost stomach of a ruminant. 



sacculus. The membranous sac connected with the cochlear duct of the ear. 



sacnun. The five fused vertebrae to which the ilium is attached. 



sagittal plane. A median longitudinal vertical section. 



Santorini's duct. The accessory duct of the pancreas. 



sarcolemma. The delicate elastic membrane which surrounds a muscle fiber. 



sarcoplasm. The interfibrillar substance of a striped muscle fiber. 



Savi's vesicles. Cranial sensory vesicles of Torpedo without external openings. 



scala media. The cochlear duct. 



