95. But passing from these perhaps questionable cases, let us glance at other cases. The mobile iris of the bird displays movements after the nerves have been divided. Even the voluntary striped muscles are not altogether motionless. Schiff divided the hypoglossus on one side, and found, of course, the tongue paralyzed on that side; but he also found that on the third day after the operation some of the muscles of that side were quivering: the agitation spread to others, till by the end of the fourth day all the fibres were _rhythmically_ contracting. From this time onwards, the contractions were incessant; though they were never able to move the tongue, because the fibres did not contract simultaneously. Schiff also observed that the hairs over the eyes and the “whiskers” of cats, rabbits, and guinea pigs were for months after section of their nerves in incessant rhythmical vibration. This was observed when the animals were asleep as when awake. Valentin records the spontaneous movements in the diaphragm of animals just killed; and this even after section of the phrenic nerve. The same movements may be seen in the operculum of fishes. Henle observed the spontaneous contractions of the intercostal muscles; which Schiff confirms, adding that the movements observed by him in cats and birds were not simply contractions of some fibres, but of all the muscles, so that three or four excised ribs rhythmically contracted and expanded. I have performed a great many experiments with a view of determining this question, but the phenomena were so variable that I refrain from adducing any,[124] and merely state the general result as one in harmony with the foregoing examples. The great variability of the phenomena depends upon the variable conditions of muscular irritability and anatomical relations. When the heart of one woman is found beating twenty-seven hours after death, while in most men and women it ceases after a few minutes, we must be prepared to find different, and even contradictory phenomena under varying unknown conditions. There is, however, a general agreement among experimenters that muscular irritability increases after separation from nerve-centres, and then quickly decreases again.