From the Wellcome Library Blog:
The Wellcome Library has introduced full text searching for a proportion of our digitised items. You can now search inside the items themselves, in addition to searching across information about the items.
You can currently search the full text of all of our digitised genetics books and Medical Officers of Health reports. This is just over a million pages in about 7,400 items. You’ll find more and more useful information as we continue to digitise and index the full text of our collections.
Direct to Wellcome Library Online Catalogue