Drawing defines form. However sometimes it is hard to see this form. Different colors and surfaces reflect light in different ways.
When taking pictures of horses it is best to do so on a hazy day to break up the sun’s rays, because the sheen on a horse’s coat caused by the reflected light from the sun inhibits the ability to discern form. I would recommend a nice medium value brown or grey horse for anatomical study. A white one will reflect too much light and a black one will not reflect enough for optimal viewing.
Picture above from, "Animal Anatomy For Artists"
by W. Ellenberger
graphite on 8.5 x 11 bond paper
CLICK ON PICK FOR SHARPER IMAGE