GENERAL STRUCTURE 



21 



is enclosed in certain membranes or coats. Certain fibers of 

 the sympathetic nervous system are surrounded by a delicate 

 homogeneous membrane, the neurolemma, and are known as 

 nonmednllatcd fibers. The fibers of the central nervous system 

 are generally distinguished by an intermediate layer of myelin 



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B 



C 



Fig. 10. — The Three Types of Cartilage: A, Hyaline; B, Elastic; C 



Fibrous. (Radasch.) 

 a, b. Outer and inner layers of perichondrium; 

 older cartilage cells; e, f, capsule surrounded by 

 lacuna. 



c, young cartilage cells; d, 

 deeply staining matrix; g. 



between the axis cylinder and the neuolemma and are known as 

 medullated fibers. The myehn sheath is more or less interrupted 

 at regular intervals by the so-called nodes of Ranvier, Nerves 

 are bundles of nerve fibers arranged in a parallel fashion and 

 enveloped in a connective-tissue sheath or epineurium. Nerves 

 carrying impressions to the central nervous system are known as 

 afferent or sensory nerves; those carrying impulses peripherally 

 are the efferent or motor nerves. 



