Graaf, R.  De succo pancreatico, or, A Physical and Anatomical Treatise on the Nature and Office of the Pancreatick Juice (1676).

One of the earliest works on pancreatic secretion.  Graaf's first published work, originally issued in Latin in 1664, details his use of artificial pancreatic fistulae to collect the pancreatic juices of dogs.  His experiments revealed the production of a small amount of juice, alkaline in nature.  This book is the first English translation, taken from the 2nd Latin edition of 1671. 

Reinier or Regnier de Graaf (1641-1673), Dutch physician, anatomist, and physiologist, is considered to be one of the creators of experimental physiology.  He published on diverse subjects, but is best known for devising the method of pancreatic fistula and for his pioneering work on the female reproductive organs.  His discoveries laid the foundation for modern sexual endocrinology.

(Sources: Garrison & Morton; Dictionary of Scientific Biography)