By this general death is meant the death of the organism as a whole, but all parts of the body do not die at the same time. The muscles and nerves may react, the heart may be kept beating, and organs of the body when removed and supplied with blood will continue to function. Certain tissues die early, and the first to succumb to the lack of oxygenated blood are the nerve cells of the brain. If respiration and circulation have ceased for as short a time as twelve minutes, life ceases in certain of these cells and cannot be restored. This is again an example of the greater vulnerability of the more highly differentiated structure in which all other forms of cell activity are subordinated to function. There are, however, pretty well authenticated cases of resuscitation after immersion in water for a longer period than twelve minutes, but these cases have not been carefully timed, and time under such conditions may seem longer than it actually is; and there is, moreover, the possibility of a slight gaseous interchange between the blood and the water in the lungs, as in the case of the fish which uses the water for an oxygen supply as the mammal does the air. There are also examples of apparent death or trances which have lasted longer, and the cases of fakirs who have been buried for prolonged periods and again restored to life. In these conditions, however, all the activities of the body are reduced to the utmost, and respiration and circulation, so feeble as to be imperceptible to ordinary observation, suffice to keep the cells living.