Abstract
Various observers (Reiss and Haurowitz, 1 Avery and Johlin, 2 Kabat and Dennis, 3 Selle and Witten, 4 and Himwich, Alexander and Fazekas 5 ) have reported that young animals are much less susceptible to anoxia and asphyxia than adults. The present studies were undertaken to determine whether the primitive respiratory mechanism (gasping) itself survives longer in the young than in the old.
Movements of the mandible of various species (dogs, cats, rabbits, and rats) were recorded mechanically following complete and rapidly induced anoxia produced by ligation of the cerebral vessels or by decapitation. In preliminary experiments it was found that the character and duration of the gasps induced by either of these methods were essentially the same and that the gasping movements of animals in which the cerebral vessels were ligated corresponded to and were simultaneous with labored respiratory movements of the trunk.
It is evident that the respiratory center of the young is much more tenacious and viable than is that of the adult, and that the survival of gasping itself is inversely proportional to age for animals up to or slightly past the weaning period. Thus, the isolated head of a rat 7 weeks of age or older gasps 5 to 8 times over a period of 10 to 20 seconds and remains motionless thereafter; whereas, the head of a younger animal may continue to gasp for many minutes.
Unlike adults, rats under 6 weeks of age display 2 periods of gasping movements: an initial series which consists of 6 to 12 gasps and lasts for a period of 20 to 80 seconds; and a second series which begins after an interval of 30 to 50 seconds following cessation of the initial or first series.
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