You can download Pathways to Pregnancy and Parturition 2nd Revised Edition by P. L. Senger free in pdf format.
This reproductive physiology textbook is used in over 140 universities around the world. It provides detailed specimen and full color graphics targeted specifically to students. Highly visual presentations. Concepts clearly presented. Relevant and updated. I used this book in my undergraduate reproduction class and now use it in my veterinary curriculum, and it’s by far the best physiology textbook out there. I will go as far to say that it’s my favorite science textbook I’ve ever owned. The pictures are incredible, the descriptions are complete and very clear, and it’s actually enjoyable to read. I highly recommend this book to anyone interested in reproductive physiology, anatomy, or animal reproduction in general.