One hundred years earlier, dogs such as Boxer, English Bulldog, and Dachshund have been well-proportioned, super healthy, and physically fit, there are markedly different variants of these breeds today.
Most of the dog breeds around today no longer look such as what the dogs seemed to look like, the process speeded up in the 20th century as more sophisticated techniques of genetic modification were discovered and modern medicines allowed breeders to inspect dogs at the genetic level, as a result, the breeds around today are different from their counterparts decades ago, these pictures of dog breed now and then provide clear proof of the effect of selective breeding.
The Science of Dogs blog has put together a side-by-side comparison of several popular dog breeds from Walter Esplin Mason's 1914 book Dogs of All Nations, showing what they look like today.
Here are some of the dogs from that blog
West Highland White Terrier