User blog comment:Gourgeist/Shingeki no Kyojin Chapter 66 Review: Wish/@comment-7418318-20150210234336

If you can become a Titan-shifter from - excuse the terminology - licking one tounge-full of serum from the ground, why did they bother with syringes? They could just drip it into the person's mouth, be done with it and still have the majority of the serum as backup or to make another person into a shifter too.

Or could it be that Rod's titan-form is incomplete due to having only part of the serum ingested?