Abstract
A simple method has been devised for the extraction of deoxyribonucleic acid from histological sections by means of the enzyme DNAse without significant loss of ribonucleic acid.
Removal of deoxyribonucleic acid by this method completely eliminated the radioautographic reactions observed over nuclei after injection of thymidine-H3. It is concluded that labelled thymidine is an adequate tracer of newly formed deoxyribonucleic acid in radioautographs.