Here is one of the best and most used medical references we have used. We have the hard back edition.
"Ship's Medicine Chest and Medical Aid at Sea"
by the US Public Health Service
http://www.operationalmedicine.org/TextbookFiles/ShipsMedicineChest.htm
Here's the description from Amazon:
The Ship’s Medicine Chest and Medical Aid at Sea is published primarily for the information and guidance of the Master and other licensed and certified crew members who may be directly or indirectly responsible for the administration of medical treatment at sea on vessels which do not carry a physician. This book attempts to describe in nontechnical language, the diseases and medical emergencies most commonly encountered while at sea and the "first aid" and "follow-up" care required until the patient can be evaluated and treated by a physician.
It must be emphasized that the care and treatment of a patient at sea is much different than while ashore. The medications and treatments suggested in this book are based on the fact that a physician is not physically available and that such treatment must be carried out by intelligent seamen and ship’s officers who have received training in the delivery of health care. It is used on fishing vessels, by outdoorsmen, explorers, and backwoodsmen as a guide when professional medical care is not available.