No abstract

More first-born pups and greater numbers of pups were born in a familiar cage having a covered nesting box than in a glass bowl, when pregnant mice at term were alternated between contrasting environments. Current theories emphasize the influence on labor of mechanical and hormonal factors; these data suggest that environmental factors also may play a role.

No abstract

Certain intermittent lighting schedules can produce heavier chickens than the traditional 14-hr. light—10-hr. dark regimen by providing for adequate food intake with minimum activity. This phenomenon is affected by behavioral control and is unaffected by restriction of feed during dark periods.

Housemice of five strains were tested repeatedly in a runway apparatus so arranged that both dimensions of gross activity could be measured. Exploratory performances showed the expected decline both within and among days of testing. On the other hand, general activity did not decrease among days. Moreover, the magnitude of correlation between the two behaviors was minimal except for one strain. These data are construed as definitive in establishing the separateness of the two categories of gross activity: general activity and exploratory behavior. Moreover, these data indicate that maze learning drug response differences reported for these strains cannot be explained by differences in activity variables.