Co2+  + S2-  ---->2CoS

         At this point, the coloration is lacks contrast and it is necessary to go through an intensifying process by using silver.  This way, the silver nitrate in presence of Cobalt Sulfide and a reduction agent such as hydroquinone is reduced to metallic silver:

(CoS)

Ag+ --------------------------> Ag 0

(Hydroquinone)

          The coloration with Cobalt Chloride allows us to make complete mountings and analyze the neuron in its totality (until its finest ramifications) and its connections with the different centers of integration inside the central nervous system.

          In this practical work, we will use as a model the ocelli system of the bug Triatoma infestans to practice this technique.  The particularity of this system is that the interneurons of first-order inside it are of easy access.  This allows us to fill the axons with Cobalt Chloride and analyze the projections of them inside the central nervous system and to locate the positions of the neural bodies.

          The assassin bug has two simple eyes, the ocelli.  These are located behind the compound eyes.  The ocelli are small photoreceptors in addition to the compound eyes.  Each ocellus is composed of a corneal lens, which is located right over the photoreceptor cells.  These cells contain a few interneurons of great diameter and some smaller ones.  These interneurons are bound with photoreceptor cells in the ocellus' neuropile, which is located at the base of the ocellus and expands to the central nervous system.

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