An unexpected doubling

"Oh that's... huh, trippy...." she says softly. You feel like something is happening down there but nothing that you can see from your angle which is mostly Dr. Black's neat blonde hair as she leans close over you. Her right hand cups your balls as her left holds her dictaphone once more, you are starting to worry about what you've let this doctor put in you. Or let this doctor gently convince you to put in yourself.

"The base of the penis is showing some unexpected growth, rapidly increasing in length..." as she speaks you feel her stroke a part of you, between your balls and cock which you know didn't exist a few minutes ago. The pleasant feeling it sends through you is not quite enough to mute your concern.
"Uh... doc what's..."
"Please don't panic, it seems that rather than doubling the length of your penis the medication has in this instance caused you to... grow a second, it looks like it will reach the same size as the original within the next minute or two..." You squirm a little in your seat trying to see what she's talking so clinically about. "Does it hurt?"
"Not at all..." you answer honestly, "is it temporary?"
You swear you see Dr. Black lick her lips but she shakes her head, swishing her hair a little "all other participants' physical changes have fully reversed once the medication has been metabolised. Despite the unique nature of your presentation I have no doubt the same will happen to you." She seems a little disappointed as she says that, underneath her professional tone. As she performs a motion that you match up to the sensation you're feeling as her stroking your second cock, you catch a glimpse of it growing rapidly between her fingers. As it reaches the size of your first, or upper cock it slows and stops. "Patient has grown from the base of his original phallus a second, identical to the first in all appreciable ways. No pain was reported." She quickly whips out her measuring tape again, quickly working around your dual members. "No size increase noted for the original and the novo phallus is identical by measurements. Testicular volume estimated at 150-170% of original." She checks the timer. "9 minutes and 12 seconds since medication administered."

She considers then a moment more as she tucks her measure away. She reaches down and flicks a switch and the chair starts to recline into the lying position. You wait, her patient patient, as she slides back onto the chair in the space between your legs, she rests on the side of her hip, looking at your cocks from the side. She reaches out with both hands and starts to pump your shafts. She spits twice and her saliva runs down your shafts and into her fists.
"How does it feel?"
She looks up at you, tone professional enough for you to pretend she's not currently pumping your throbbing cocks, plural.
"Good..." You speak softly worried it'll stop whatever is happening to tell her. "I can feel both of your hands, I can tell it's different cocks and ah yeah... it's nice."
"Faster?"
You just nod to this and she obliges, her hands working alternatly, her left caressing a tip while the right squeezes the other base. You softly moan watching her. She leans forwards and her mouth returns, this time taking in your lower cock in. As she bobs her head down it your upper cock brushes over her nose. Her beautiful eyes look up at you from the other side of your cock and the precum and saliva coating it transfers to her nose and forehead as she works underneath it. She gags slightly, looking prettily up at you and you decide you can rest a hand on her head now. This does not seem professional enough to worry about decorum anymore. **** on your cock is not a research protocol you are certain. You gently push her down, encouraging her to take your second cock into her throat and she moans softly against it, her fist squeezing the cock between the two of you. You can't help but think Dr. Black is enjoying you guiding her down your cock like a whore.

As she gags again she begins to pull up and you release your grip on her blonde hair, her eyes water slightly as her lips leave the head of your lower cock and a strand of saliva connects her lips to the head still. She attempts to wrap her hand around both your cocks and with thumb and fingers extended she just about manages it. She squeezes them together, looks down at the two cock heads pointed up at her. Looks at you with a gleam in her eye.
"You want to **** on both of them?"
She licks her lips and nods, "pull me down?"
You rest your hands on her head again, gently twine your fingers into the blonde hair, her blue eyes on you as Dr. Black opens her mouth, as wide as she can. Her lips stretch around both of your cocks and she tries to squeeze them together. The feeling of them rubbing against each other odd, but pleasant. You apply pressure to her head, encouraging her down. Her tongue licks over your lower shaft and she squeezes it between the two of them. She gags a little but shows no sign she needs to be let up so you continue to push her down, the substantial girth of your twin cocks pushing into her throat. You push deeper, moaning softly at the feeling of being squeezed like this but as she starts to cough and splutter, most of the way down your shaft you release her.

As she pulls back up she's panting, her chest rising and falling, her cleavage glistening under her dress. She smiles and nods to herself, somehow you can imagine some sort of achievement being ticked off in her mind. can fit two cocks in my mouth. Suddenly she leans forwards and spits on your upper cock, then grabbing it and pumping. Both of her hands working your shaft, twisting and squeezing. She leans her face close, avoiding the lower cock and delicately licking the tip occasionally.
"Cum on my face, I want you to cum on my face. Make me look so pretty covered your cum, let me drain your heavy fucking balls, give me your tasty seed. Please please please."

The sudden slew of dirty talk pouring out of the doctors mouth doesn't give you much choice, especially with the way she's pumping you. The cock in her hand twitches and your seed splatters out over her pretty face. She smiles, slowly pumping the last of it out you so it drains down your shaft as you start to soften. She watches and shifts her hand to your lower cock, continuing to stand tall and throb in her hand as the other sinks down.
"Climax appears possible independently from each phallus with a refractory period affecting only one at a time." Oh, that was all still research, sort of. You're still a research subject to her, even if you are a research subject that just came on her face. The dirty talk was just a studied way to get you to cum quickly, she's probably not as slutty as you were thinking for a second there, probably. Although that doesn't really explain why she had to try to fit both in her mouth...

As she starts to pump your lower cock with more speed you realise you are not done cumming for this study just yet though. She grins at you, "don't keep me waiting. Don't you want to go again? You think one load is enough for me? Be my good boy, come on." If anything it's even quicker this time as you unload onto her again. This time she licks her lips, swallowing some of your seed as it runs down her face. That definitely doesn't feel like it should be required for the research. She better not start recording the taste right now... She shifts her hand again, back to the upper cock, hardened once more.

"Would you say you can normally get hard again this quickly?" Professional tone again giving you whiplash, are you test subject or her good boy?
"Ah, no I wouldn't say so..."
She nods, "hypothesised decreased refractory period through stimulation of the alternative penis," She uses both hands again, squeezing your hard and your softened cock against each other as she pumps until you get hard again.

She removes her hands, bites her lip and is more shy when she speaks again. Lacking the previous confidence in her accented words. "I think, that'll cover all the salient questions for now... but we still have some time. And obviously two penis'... well it uh... raises some possibilities that might previously have been, well, restrained to world of fantasy as it were... if you see what I mean." She sheds the lab coat and dropped it to the floor, her fingers fiddle with the bottom of her dress.
"You want to have sex with me?" Something about how she stumbles her way though her explaination makes you feel more confident. Or maybe having two cocks does that. Or maybe the way she's looking at them.
She nods and quickly, as if to prevent herself losing her nerve, she stands and pulls her dress up and over her head, throwing it behind the desk. She stands before you in just a pair of yellow panties which she quickly pulls down before you have a chance to appreciate them. She walks to the desk letting you watch the way her hips sway and then bends over to open a drawer. For a second you want to have her right there, bent over the desk but you hesitate and she turns and smiles. She shows you the bottle of lube she's pulled from the desk drawer and she walks back to you. You might as well let her continue, she clearly has a plan. And you're confident you'll like it.