I always like to see a new creative use of a rattlesnake in a movie, especially a Western, where most rattlesnakes are just there as an obstacle to be killed by someone, and this movie has a couple uses I hadn't seen before. It's a pretty good coming of age Western that feels realistic with none of the gunfighting shtick that so many of the older Westerns rely - the kind with quick-draw gunfighters so fast and accurate they can shoot a hole in the middle of a coin thrown up into the air and other wild west mythical nonsense like that. But it does have a lot of gunfighting and there's no way there was as much violence and shooting on a typical cattle drive as there is in this movie. If there was, there wouldn't have been any cowboys left alive to punch the cattle.
A young farmboy, Ben, wants to be a cowboy so he gets hiself hired as a cook's assistant on Mr. Culpepper's cattle drive north to Colorado. On the journey he learns how to kill and drink whisky and do all the things the other cowboys do like - well, killing and drinking whisky is most of what they do. One night when the cowboys are sleeping, a group of cattle rustlers scare the cattle into a stampede by shaking some rattlesnake rattles. This is pretty unlikely, because even if you sew a bunch of rattle strings together like they did to make really long rattles, then hold two of them in each hand, it still probably wouldn't make enough noise to scare the herd. But it's inventive so I'll believe it anyway.
There's also a live rattlesnake in the movie. Those same cattle rustlers killed four of Culpepper's men when he fought them to get back his cattle, so he sends Ben to a saloon in a small town to find a man who can bring 3 other men and come finish the drive. In the saloon he sees the bartender put a large glass bottle with a rattlesnake in it on the bar and bet a customer that he can't keep his hand on the glass when the snake strikes. The man loses the bet and slaps and curses his hand for being a coward. I don't know if this betting game with the snake is a real one, but it seems entirely possible. I'll bet I'd pull my hand away, too.
I'm not entirely sure what kind of rattlesnake is in the jar. The movie was made in Arizona and New Mexico, so odds are it's a Western Diamond-backed Rattlesnake, but we don't see enough of the snake to know that for sure.