Answer:
for testing differnt cures on animals
Explanation:
Here are some of the animals that have names that start with S: seal, sheep, skunk, sloth, sparrow, squirrel, swan, salamander, scorpion, serval, snake, spider, stork, etc.
Hope this helps :)
The andswer to the question is Endocrinology!
The invention that allowed scientists to study cells for the first time is the Microscope