This chapter discusses the characteristics of human fetal reflexes at different developmental periods are and reviews the sequence for the development of cutaneous sensitivity. Human fetal reflexes resulting from the stimulation of sensory trigeminal areas are classified into (1) avoiding and/or protective reflexes and (2) those that function later in feeding.
The sequence of development of reflexes of each type, with the area from which it is elicited, is tabulated in the chapter. The development of the spinal tract and the peripheral receptors of the trigeminal nerve and the differentiation of the sensory trigeminal nuclear complex are correlated with the appearance of the various fetal reflexes elicitable by stimulation of this nerve.
The chapter considers the known developmental relations for the motor neurons involved in these reflexes and discusses the probable reflex arc for the first reflexes from trigeminal stimulation. Reflexes obtained by stimulating the upper and lower extremities are discussed and correlated with known nervous system development.
The chapter also tabulates the correlations with the development of peripheral exteroceptive and proprioceptive receptors and with motor end plate differentiation. The reflexes elicited by anal and genital stimulation are discussed and the latter correlated with the differentiation of the peripheral receptors. The differences in the reflexes obtained on double simultaneous stimulation before and after 14 weeks of menstrual age are discussed.
