432 THE ORGANS 



connective tissue still remaining constitutes the sheath of Henle. 

 The space between the neurilemma and sheath of Henle has been 

 described as a lymph space communicating with the rest of the 

 lymphatic system of the nerve. On emerging from the central 

 nervous system, the root libres receive an investment of connec- 

 tive tissue (endoneurium and perineurium) as they pass through 

 the pia mater. This is reinforced by additional connective tissue 

 epineurium,) as the nerve passes through the dura mater. For 

 description of medullated and non-medullated nerve fibres see 

 Chap. VI. 



TECHNIC 



Fix a medium-sized nerve, such as the human radial or ulnar, by suspending 

 it, with a weight attached to the lower end, in formalin-Miiller's fluid (technic 

 6, p. 7). Stain transverse sections in haematoxylin-picro-acid-fuchsin (technic 

 3, p. 21), or haematoxylin-eosin (technic i, p. 20), and mount in balsam. Pieces 

 of nerve should also be fixed in osmic acid imbedded, cut, and mounted without 

 further staining. Pieces of fresh nerve may be tested and examined without 

 staining. 



THE AFFERENT PERIPHERAL NEURONES 



These comprise, as already stated, the bodies and processes of 

 the cerebro-spinal ganghon cells or cerebro-spinal ganghonic neurones, 

 probably some of the sympathetic ganglion cells, certain cells of the 

 retina and certain cells of the olfactory mucous membrane. The 

 two last named are described in connection with the organs of special 

 sense. 



The Cerebro-spinal Ganglia 



A cerebro-spinal ganghon contains the bodies of the cerebro-spinal 

 ganglionic neurones whose processes form the afferent root of the 

 cerebro-spinal nerve. It lies in the dorsal root, a dorsal root being 

 that part of the nerve which lies between the exit of the dorsal root 

 fibres from the cord and their junction with the ventral root. 

 Each ganglion is surrounded by a connective-tissue capsule which is 

 continuous with the perineurium and epineurium of the peripheral 

 nerves. (Fig. 297.) From this capsule connective-tissue trabeculae 

 extend into the ganglion, forming a connective-tissue framework. 

 Within the ganglion the nerve cells are separated into irregular groups 

 by strands of connective tissue and by bundles of nerve fibres. 

 Each ganglion cell contains a centrally located nucleus and a dis- 



