The similarity that both Ross and Treves use to describe John Merrick is that they both call him an elephant man.
This refers to the use of words to show the features and characteristics of a person that creates a mental image.
Hence, we can see that from the complete text, John Merrick has a birth defect that makes him have skull bone outgrowth, with skin protruding from his face and an overgrown right arm and this makes people treat him badly and call him the Elephant Man.
Read more about Elephant Man here:
https://brainly.com/question/17252139
#SPJ1