From the Animation Archive (Broken Link):
To create new model sheets for each of the characters in “Get A Horse!,” Disney Animation hand-drawn artist Eric Goldberg studied early Mickey films.
The Animation Archive website is a treasure trove of animation related artwork: Check it out (Broken Link).
Model Sheets by Eric Larson:
Also see: This post on the a video game under development that nails the look of early to mid 1930s animation style.