THE RATE OF TRANSMISSION IN THE NERVE NET OF THE C?LENTERATES

Nerve net transmission in Metridium at 21°C. varies from 121 to 146 mm. per second.     

TEMPERATURE COEFFICIENT OF THE ACTION OF β-RAYS UPON THE EGG OF NEREIS

The temperature coefficient of the action of β-rays from radium upon the egg of Nereis lies between 1.1 and 1.2. This is of a magnitude characteristic of photochemical reactions.     

METAMORPHOSIS OF THE LARVA OF THE POLYCHAETE ARENICOLA CRISTATA. MORPHOLOGY OF THE ‘HOUR-GLASS’ STAGE

The constricted ‘waist’ of the metamorphosing larva of the polychaete Arenicola cristata is described, using light and electron microscopy. The constriction is shown to be the consequence of the discharge and collapse of a post-trochal ring of epithelial cells which remain as functional components of the post-metamorphic juvenile. Morphological differentiation of neuro-effector and interneuronal contacts is initiated at this time. Muscular and neural changes are discussed in terms of their role in effecting metamorphosis.     

A STUDY OF INFLATION OF THE LUNGS OF THE NEWBORN—A Preliminary Report

There seems to be no reasonable doubt that the lungs in a newborn expand progressively during the first few days of life. Some degree of atelectasis seems to be perfectly normal. This is indicated by a number of roentgenographic studies (including those here reported); by the reported findings of pathologists; by the fact that in experimental animals the lungs inflated very unevenly; and by the fact that aeration of only a portion of the lung is needed for complete oxygenation of the blood. The relation of atelectasis to neonatal death is not entirely clear and is probably not always the same. The infant may die from other causes before the lungs are fully expanded. Atelectasis may develop secondarily to other debilitating conditions. The frequent coincidence of prematurity and extensive atelectasis is impressive. It may be that the lungs are so incompletely formed that they cannot expand. On the other hand, atelectasis and massive collapse in the adult is a serious condition and there seems to be no good reason to suppose that this cannot also occur in infants and be serious per se.The air pressures found necessary to expand the lungs in rabbit fetuses were found to be about ten times what adult humans use in quiet respiration and were of about the same magnitude as the pressures found necessary to expand the lungs of stillborn humans. An attempt to produce atelectasis in newborn rabbits by chilling was most inconclusive. Atelectasis did develop in three of 15 animals used in the experiment, but the relation to chilling was not at all clear.