Section 151A. Whoever, himself or by his agent, sells or exposes or offers for sale in a retail store horse meat which does not have attached thereto in a conspicuous place a sign or label bearing in printed letters in a straight line of plain gothic type not less than one inch high the words ”horse meat”, and whoever serves horse meat or causes it to be served at any lunch counter or in any restaurant, hotel, boarding house, convalescent home, hospital or like place, to a guest, patron or patient thereof, without notifying said guest, patron or patient that horse meat is being served to him shall be punished by a fine of not less than ten nor more than fifty dollars.