"lets see that back side of your, with a good bit of tail to boot" Sam saids as you turn yourselve over, your ass in your friends direction as you focus your transformation on your backside and to some degree your spine.
you control your breathing as you feel your tail bone begin to grow out, forming a small flushy numb at the base of your spine. once you have a point of exit for your spine you focus on growing it out, trying to maintain your breathing as you feel your spain pulled down your back and hear the vertebrae pop, crack and reform as the tail goes from fleshy to leathery in texture as as it began to thicken in mass.
in a matter of minutes the tail is already 3 feet long and moving freely on its own as you feel sweat going down your back, brusing up agains the light fuss forming along your spine and ass cheeks. your feel some changes bleed to your backside as your anus has grown larger and darker and your ass cheeks thicken with muscles.
"boy, your getting thick there, and that tail is being a bit saggestive there." Sam saids jokingly as you look to see that your tail is stray up in the air like its inviting someone to mount your rodent backside.
"the changes this slow can be very...arousing, a way the body encourage me to change faster" you reply as you sak ask you to take different suggestive poses of your backside and tail for his anatomy study.