Senescent-decliue in the nervous-system functions is very frequently atbibuted to age-related neurone-loss. Processes and mechanisms involved in neuro- degeneration form part of the structural frame-work for interpreting the functional consequences. The literature concerning this matter are confusing and contradicting. The behaviour of cranial nerve ganglia was studied using neuro-histological techniques. On the evidence available in the present study, the dark cells are considered as active ones; the light cells are considered as those which have failed to establish functional projections, inactive, dying, dead or degenerating ones. Probably it is during the me- dium-sized stage of cell growth, the peripheral and central processes (of axons) begin to grow from the cell body and attempt to get established in their projection fields. The light cells have appeared among the very-small cells just on the day of hatching. This probably signifies the possible attempt to elinlinate the growing cells since they are no longer needed to replace larger categories of cells which have already well- developed neuronat connections at this stage. It is assumed that the time of appear- ance of light cells might be indirectly related to the onset of establishment of active functional connections of neurones and to the functional importance of the organs which it supplies. KEYWORDS: Neurone-Loss and Ageing, Dark and Light Neurones, Sensory and Autonomic Ganglia