GLOSSARY 68l 



neurobiotaxis. The migration of the cell bodies of neurons towards the source of 



stimulation. 

 neuroblast. The embryonic neural cell which forms an axon process. 

 neuro-epithelial cell. A sensory receptor cell the body of which is located in an 



epithelium. 

 neurofibrillae. The fine fibrils within a neuron. 

 neurogenesis. The differentiation of nervous tissue in ontogenesis. 

 neuroglia. The ectodermal supporting tissue of the central nervous system. 

 neurohumor. A nerve secretion which stimulates an effector cell. 

 neuromast. A cluster of sensory cells in the skin such as is represented in a lateral line 



organ. 

 neuromere. An embryonic segmental division of the central nervous system. 

 neuromuscular spindle. Specialized sense organs located in muscles. 

 neuron. The functional unit of the nervous system. 

 neuropore. The anterior opening of the embryonic neural tube. 



neurosensory cell. A sensory or receptor cell the cell body of which lies in an epithelium. 

 neurostoma. The hjpothetical mouth (Delsman) of vertebrate ancestors, 'which is 



represented in the neuropore of chordate embryos. 

 neurotendinous spindle. A special type of sensory nerve termination connected with 



a tendon. 

 neutrophile. A blood cell with an affinity for neutral stains. 

 Nissl bodies. Large protein granules with an affinity for basic dyes found in nerve 



cells. 

 nodosum ganglion. The ganglion of the vagus below the jugular ganglion. 

 non-deciduate placenta. The type of mammalian placenta which does not involve the 



uterine mucosa at birth. 

 non-meduUated. Devoid of myelin sheath. 



Nordic. The blond teutonic type of man of northern Europe and Africa, 

 normoblast. A nucleated stage in the histogenesis of a red blood corpuscle. 

 notochord. The axial rod between the chordate nervous system and the dorsal aorta, 

 nuchal. Pertaining to the nape of the neck. 



obturator foramen. The opening between the pubis and ischium. 



occipital lobe. The posterior lobe of the cerebral hemispheres. 



occlusion. The state of being closed. 



odontoblast. One of the dentine-secreting cells. 



odontoid process. The tooth-like process of the axis (epistropheus) vertebra. 



oestrus (estrus). The period of "heat" or receptivity in the female. 



olecranon process. The process of the ulna at the elbow. 



oliva. A prominence of the medulla oblongata lateral to the pyramid. 



omasum (psalterium). The third division of the ruminant stomach. 



omentum. A sac formed by the doubling of the mesentery. 



ontogenesis. The development of the individual from the egg. 



oocyte. The immature egg. 



operculum. The gill-cover of fishes. 



opisthonephros. The posterior metanephros-like portion of the mesonephros of 



anamnia. 

 optic vesicle. The hollow lateral outpocketing of the forebrain which forms the retinal 



and pigment layers of the eye. 

 oral hood. The funnel-like membrane which in Amphioxus bears the tentacles. 

 orbit. The bony socket which surrounds the eye. 

 OS uteri. The orifice of the uterus. 



