§ 51. Milk inspection. The commissioner or his agent, in inspecting milk for the purpose of analysis to determine the percentage of fat or other milk solids, shall take duplicate samples thereof and shall seal both samples, and shall tender, and, if accepted, deliver one sample to the person from whom the milk was taken. When samples are taken from the producer of the milk sampled or his agent, at a place other than the dairy where the milk was produced, the commissioner or his agent shall within ten days thereafter, with the consent of the producer, take duplicate samples of the mixed milk of the herd of cows from which the milk first sampled was drawn, and shall deliver one such sample to the producer or his agent and shall submit the other to analysis. If upon analysis it proves to contain no higher percentage of milk solids, or no higher percentage of fat, or has no lower freezing temperature than the sample first taken, then no action shall lie against the producer for violation of standards as established by the commissioner pursuant to the provisions of section forty-six-a. If the producer refuses to allow such herd sample to be taken, then the producer shall be precluded from offering any evidence that the milk from which the first sample was taken was just as it came from the cow. Where a sample of milk taken by the commissioner or his agent consists of the entire contents of a container unopened at the time of taking, no duplicate need be taken or tendered or delivered.