The nerves with their muscles obey the tendons as soldiers obey the officers, and the tendons obey the Common [central] Sense as the officers obey the general. [27] Thus the joint of the bones obeys the nerve, and the nerve the muscle, and the muscle the tendon and the tendon the Common Sense. And the Common Sense is the seat of the soul [28], and memory is its ammunition, and the impressibility is its referendary since the sense waits on the soul and not the soul on the sense. And where the sense that ministers to the soul is not at the service of the soul, all the functions of that sense are also wanting in that man's life, as is seen in those born mute and blind. [Footnote: The peculiar use of the words _nervo_, _muscolo_, _corda_, _senso comune_, which are here literally rendered by nerve, muscle cord or tendon and Common Sense may be understood from lines 27 and 28.] On involuntary muscular action. 839. HOW THE NERVES SOMETIMES ACT OF THEMSELVES WITHOUT ANY COMMANDS FROM THE OTHER FUNCTIONS OF THE SOUL. This is most plainly seen; for you will see palsied and shivering persons move, and their trembling limbs, as their head and hands, quake without leave from their soul and their soul with all its power cannot prevent their members from trembling. The same thing happens in falling sickness, or in parts that have been cut off, as in the tails of lizards. The idea or imagination is the helm and guiding-rein of the senses, because the thing conceived of moves the sense. Pre-imagining, is imagining the things that are to be. Post-imagining, is imagining the things that are past. Miscellaneous physiological observations (840-842). 840. There are four Powers: memory and intellect, desire and covetousness. The two first are mental and the others sensual. The three senses: sight, hearing and smell cannot well be prevented; touch and taste not at all. Smell is connected with taste in dogs and other gluttonous animals. 841. I reveal to men the origin of the first, or perhaps second cause of their existence. 842. Lust is the cause of generation. Appetite is the support of life. Fear or timidity is the prolongation of life and preservation of its instruments. The laws of nutrition and the support of life (843-848). 843. HOW THE BODY OF ANIMALS IS CONSTANTLY DYING AND BEING RENEWED.