Why is Joe compared to horses?

In paragraph 7, Joe Pervin, the eldest of the
family, is compared to the massive draft horses. These are slow but strong (having a
“slumberous strength” [paragraph 6]), and are in harness, as Joe will be once he marries
the daughter of the steward of the nearby estate. In paragraph 20, Joe is also compared
to horses because of his appearance when walking and speaking. In addition, another
brother, Fred Henry (paragraph 11), is compared to horses, for he is under the control
“of the situations of life,” even though he masters horses easily. Because the horses,
though strong, need the external control of reins, the idea seems to be that those
without love are without the strength they need to guide their own destinies.