As a current dairy farm worker and former milk tester (nowadays rebranded as "DHIA technician") I was beyond thrilled to see this pic! Thanks, Shorpy!

The age-old symbol of a cat happily lapping up a bowl of milk may have been perpetuated by unknowing, non-scientific poets, writers and Mother Goose fans, but for the past fifty years or so, we have been told by veterinarians and cat experts that cats should drink only water after they have been weaned off their mom's milk unless you buy them cat milk, which is an actual product sold in pet shops, etc. as a rare and only occasional treat (but not regularly).Just like lactose-intolerant humans, cats usually cannot handle the lactose and some other elements in milk and may suffer gastro-intestinal problems from drinking it. Some of the results of their stomach distress are not pretty and the cat suffers pain and discomfort too. This was told to me by a veterinarian and I realize that some people do not buy into this, but that's my story and I'm sticking to it.

The gentleman is performing a Babcock test to determine the fat content of the milk. The device in the right of the photo is a centrifuge for separating the fat from the water and sulfuric acid that he previously added. The fat floats into the tube neck, where he can directly measure its percentage.

The kittens are there for the vital taste test!

I think you mean Milk testers, the apprentice has some assistants.

[Um, the apprentice is the kitten. - Dave]