146 



NERVOUS TISSUES 



and spinal cord, and also in the olfactory nerves, the optic chiasm, and 

 the retina of the adult. 



The supporting tissues of the central nervous system include, besides 

 the neuroglia, numerous bands or trabeculse of fibrous connective tissue, 



FIG. 161. NEUROGLIA CELLS AND FIBERS FROM THE SPINAL CORD OF AN ELEPHANT. 



The letters indicate various types of neuroglia cells. /, a leukocyte. Benda's stain. 

 X 940. (After Hardesty.) 



which push inward from the pia mater, carrying with them the vascular 

 branches for the supply of the nervous tissues, and which penetrate 

 deeply into the substances of the spinal cord and brain. 



NERVE TRUNKS 



Structure. The nerve fibers of the peripheral nervous system are 

 united into bundles to form the nerve trunks or nerves. Each nerve 

 is surrounded by a heavy connective tissue sheath, the epineurium, which 

 sends trabecula-like septa into the nerve. 'These septa subdivide the 

 nerve trunk into smaller bundles of nerve fibers, the funiculi. The 

 funiculus forms a compact bundle of nerve fibers, and is in turn invested 

 with a sheath of dense connective tissue, the perineurium. Hence the 



