With regard to the first omission--the Muscular Feelings,--a further advance has been found requisite. Instead of adding these to the list, as a sixth sense, they are made a genus apart {4} and put in contrast to the Sensations as commonly understood. They are the feelings of our ACTIVITY, of the Active side of our nature, and are in relation to the Motor or Outcarrying nerves of the body. The Sensations proper, such as Smell and Hearing, are the feelings of our RECEPTIVITY, or Passivity, and arise in connection with the Sentient, or Incarrying nerves. In the exercise of the senses, however, a muscular element is almost always combined. This is conspicuous in Touch, which is most frequently accompanied with movements of the hand, or other parts touched; it is also the case with Sight, there being six muscles constantly engaged in moving the eye-ball. There is least muscularity in Hearing and Smell, but in neither is it wholly absent. Thus in Hearing, there are certain small muscles for adjusting the tightness of the membrane of the tympanum; apart from which, there are movements of the head in conjunction with hearing. So in Smell; the sniffing action with the breath is muscular. Nevertheless, it is easy to separate, in all the senses, the passive and proper sensibility of the sense, (called by Hamilton the _idiopathic_ sensibility) from the active accompaniment. We can make experiments upon passive touch, or pure contact; we can isolate in our consciousness the optical sensibility of the eye; we can eliminate activity from the ear; and we can attend to the sensations of smell in their pure passivity. The best course of proceeding is to deal with Muscularity apart, in the first instance, and to give it the priority in the order of exposition. Chronologically it is an earlier fact of our being; we move before we feel; there is an inborn energy of action in the animal system, which goes out, as it were, and meets the objects of sensation. This is one reason of priority. Another is the fact just stated that movement accompanies all the senses, or is a common factor in sensation. To discuss its peculiar sensibility is thus a preparation for treating of the senses.