[Evolution of the H index in infants from birth (author's transl)]

The technique of using Hoffmann's soleus reflex can be simplified and carried out more rapidly if only the M and H latences are recorded. The calculation of the H index from these latences by using the formula (formula, see text), can eliminate variations due to morphotype and tends to express an overall, sensory-motor, proximal conduction rate of the reflex arc. Recordings were made in 50 normal infants aged from 0 to 7 years and two phases of evolution of the H index were observed during this period of change. 1. a rapid, practically linear increase as a function of age up to 18 months: y (IH) = 3.6 X (month) + 27.5. 2. a second phase during which there is little correlation with the age, but, on the contrary, there is a very significant and constant relationship, continuing up to adult life, between the interval (H--M) and the height of the subject: y (H--M) ms = 0.125 X (height in cm) + 3. These results can be used to calculate the theoretical reference H index throughout the growth period of infants.