[Cardiac fibrillation in early ontogeny in animals born mature and immature]

The processes of spontaneous reversible fibrillation were compared in mature-born (guinea pigs, hens and cocks) and in immature-born animals (cats, dogs and rats). An increase in duration of the fibrillation in immature-born animals was most significant in the period of recovery of sight which is associated with an increasing parasympathetic influences.