Section 25-5-58
Effect of preexisting injuries or infirmities.
If the degree or duration of disability resulting from an accident is increased or prolonged because of a preexisting injury or infirmity, the employer shall be liable only for the disability that would have resulted from the accident had the earlier injury or infirmity not existed.
(Acts 1919, No. 245, p. 206; Code 1923, §7561; Code 1940, T. 26, §288.)