the Histological Changes in Nerve Cells Due to Total Temporary Anæmia of the Central Nervous System

With the return of the circulation, dilation of the pericellular lymph space and slight swelling of the cell body occurs, disappearing as recovery progresses. Chromatolysis, as evidenced by poor affinity for stains, clumping, diffuse staining, and breaking into dust-like particles, induced by anaemia, is not necessarily fatal. Death of the cell is not shown histologically when tissue is removed and fixed immediately after the experiment. Some time must elapse for the detection of the vacuolation, displacement of the nucleus and solution of the chromatic substance, indicative of profound changes. Neurones from different regions as well as neurones of the same region differ in degree of resistance to anaemia. The small pyramidal cells are the most susceptible, and then come the Purkinje cells, cells of the medulla oblongata, retina, cervical cord, lumbar cord, spinal ganglia and, most resistant of all, the sympathetic ganglion cells. Failure to resuscitate animals after anaemia of the central nervous system is probably due to the destruction of many of the cells of the vital centers (vaso-motor and respiratory) which do not have histological peculiarities by which they may be defined. Death, however, of a few cells of any center does not necessarily mean the total loss of function of that center, since the remaining cells may be sufficient to discharge the function of the center.