Abstract
Despite the many observations reported on survival of tissues and organs, little information is available concerning the influence of age on survival time. Several observers 1-5 have reported that young animals are more resistant to anoxia and asphyxia than are adults, and Selle and Witten 6 found that the primitive respiratory mechanism (gasping) itself survives much longer in young animals than in old. Thus, the head of a new-born rat or dog gasps 40 to 80 times during a period of 30 to 60 minutes following ligation of the cerebral vessels or decapitation; the head of a half-grown or adult animal ceases gasping within a few seconds.
The present studies were undertaken to determine whether the anoxic survivals of other physiological processes, such as pupillary responses, trunk reflexes and heart action, parallel that of the respiratory mechanism.
Survival of the gasping mechanism was determined as described previously. 6 Maximal dilatation of the pupil was taken to be a satisfactory indication of cessation of pupillary activity. Following the onset of anoxia the pupils constrict to pin point size. Later they dilate and for a time only respond to bright light. The duration of trunk reflexes (movement of tail or foot) was determined by the application of painful induction shocks to cutaneous areas of the abdomen and foot. To follow cardiac beats, the heart was exposed by a midline incision of the chest within 2 minutes after spinal transection or after thoracic respiration had ceased.
Results on 3 series of animals are given in the accompanying table. The remarkable survival of the respiratory mechanism in young animals is obviously not unique; other physiological processes survive similarly.
In early age groups the survival of trunk reflexes is about two-thirds that of gasping; in the older age groups there is no clear difference.
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