Which of these special nerve cells in the spinal cord carries messages to and from the brain?

The central nervous system is a wide network of neurons which transmits signal to each other through synapses. These are all electrochemical reactions that occur in the brain and the spinal cord. 

There are three types of neurons according to their functions. The sensory neurons are responsible to carry all signals from the rest of the body to the brain. On the other hand, motor neurons carries signals from the brain to the outer parts of the body. The third type is called the associations nerves which connect signals between the sensory and motor neurons.

The answer is joseph is observing the colour of the reaction mixture to see whether proteins are present in the given solution.