The mechanical properties of the in vivo dermis were measured by means of a torque applied to the skin. The resulting deformation of 2-6 degrees, including the immediate and delayed visco-elastic components, as well as the relaxation were measured, and the raw values corrected for a constant skin thickness. The experiment performed on 138 individuals from 3 to 89 years old revealed a diminished elasticity and stretchability after the age of 30, associated with an increase in the visco-elastic component. The Young's modulus doubles with age. The results are discussed in terms of the various models proposed to explain dermal structure.

The response of the forearm skin to a 9 . 10(-3) N . m torque was measured on 141 subjects aged 3-89 years. The results for each age class were adjusted to a skin thickness of 1 mm by use of a skinfold caliper. Results indicate a maximum skin thickness around the age of 40 years. Standardised skin extensibility decreases with age, the skin of females being less extensible than that of males. These results, which should be considered in relation to the total water content of the skin, are compared to those of other papers dealing with this subject.