To the OP - I was forced to formula feed, so don't have quite the same experience as you. I found that ds dropped a couple of feeds, having four a day between 9mths and 1yr. At a year I changed him gradually on to cows milk, and he has a drink with every meal and a cup of warm milk at bedtime, so still four feeds in theory. He is not 19mths btw. Just go with what your ds wants - he'll know how hungry he is.
To Choclover - it is a very bad idea to force any child to eat more than they might want, even if you aren't actively forcing the food down their throats.
First of all, you could be encouraging them not to listen to their bodies' natural "full" signals, which come around 20 mins after starting to eat. If a child has to eat quickly and finish their meal, they don't feel these signals, or learn to ignore them. This can cause problems with obesity in later life.
Secondly, by obsessing over the amount of food eaten, you could cause your children to think about food as an big problematic issue.
Please read this link, especially the bits near the bottom about listening to your child. In fact, here's a selected paragraph -
"Some parents think that not letting kids feed themselves is for the best, but it takes away control that rightfully belongs to kids at this age. They need to decide whether to eat, what they will eat, and how much to eat ? this is how they learn to recognize the internal cues that tell them when they're hungry and when they're full. Just as important, toddlers need to learn and practice the mechanics of feeding themselves."