Complex sentence: Through experiments on mammals he proved what the role of the seminal vesicles were in regulating the reproductive function in males; rabbits had pieces of PVC piping inserted into the seminal vesicles, stimulating the barroceptors inside.
Split into simpler sentences: Through experiments on mammals he proved what the role of the seminal vesicles were in regulating the reproductive function in males. An experiment was done where rabbits had pieces of PVC piping inserted into the seminal vesicles, stimulating the barroceptors inside.