324 BRAIN MECHANISMS AND LEARNING 



The term 'synaptic microvesiclcs' docs not imply more than calhng the 

 mitochondria of the motor plates and the synapses that contain them 

 synaptic mitochondria. It must be borne in nnnd that these substructures 

 do not exist at all synaptic levels and that, furthermore, there are 

 synapses without special groupings of mitochondria or microvesicles. 



It is our opinion that a synapse is characterized by disavitiuiiity and by 

 coiitioiiity\ the contact between membranes is very close, but lacks fusion. 











.1 







pa^qsyn. 's^ 





/ 



Fig. 15 

 Parasynapses (II) — Neurone of the cervical spinal cord of adult man 

 showing the terminal fibres of the perisomatic axonic plexus contacting 

 with each other. 



the space between them being measured in Angstroms. Nevertheless, the 

 contact of membranes alone is not a sufficient criterion of a synapse; the 

 nature of those membranes must also be considered because one of them at 

 least must be nervous; excluding neuroglial contacts which are probably 

 insulation contacts only and therefore not synaptic. 



Therefore, we propose the following concept: ..4 synapse is an anatoiiii- 

 cally close and finictionally operant contact between nienibranes, one of them, at 

 least, beinii of a nen'oiis nature. 



Many questions remain unanswered: What is the functional difference 



