There are no locks on the doors or windows, and only one route of egress in the case of an emergency.
After reaching this point the next thing is to return to the entrance, when it is found that egress is as difficult as ingress.
A tadpole is the larva of a tailless Batrachian after the loss of the external gills and before the egress of the fore limbs (except in the aberrant Xenopus) and the resorption of the tail.
The fore limbs grow simultaneously, and even more rapidly, but remain concealed within a diverticulum of the branchial chambers until fully formed, when they burst through the skin (unless the left spiraculum be utilized for the egress of the corresponding limb).
The application of vestibules is practically limited to trains making long journeys, as it is an obstruction to the free ingress and egress of passengers on local trains that make frequent stops.