Development of the labyrinthine receptors in the guinea pig, cat and dog.

Light and electron microscope observations were made on the vestibular receptors in fetal guinea pigs and cats, and in kittens and puppies. In the guinea pig hair cells were recognizable by 30 DBB (days before birth), myelinated preganglionary nerve fibers by 25 DBB, and neuro-epithelial synapses by 15 DBB. These observations can be correlated with the early development of the righting reflex in fetal guinea pig. Similar ultrastructural observations were made on cats and dogs at different times in development. A direct comparison between development in the vestibular system and the auditory system is possible since development of the organ of Corti in the same animals has previously been documented.