The first plaintiff in this suit is the widow of one Duraiswamy Mudaliar and the second plaintiff is her son. Duraiswamy Mudaliar is said have started a business about the year 1934 of manufacturing tooth powder under the name Pyorrhea Tooth Powder. The tooth powder was packed in paper envelopes and tin containers with a trade mark the principal features of which were the picture of a human face with open mouth showing diseased gums, super imposed with the numeral 1431. In the course of a few years the tooth powder became very popular, being sold all over South India and even in far off places like Malaya. In 1935, a declaration of ownership of the Plaintiff’s trade mark was filed before the Presidency Magistrate’s Court, Calcutta. This declaration of ownership was registered under the numeral 1431 of 1935. Thereafter, the founder Duraiswamy Mudaliar is said to have added the words "Registered No. 1431 as part of his trade mark. In 1937 the founder altered the trade mark by adopting a red and green label wherein his own bust portrait appeared at the left-hand bottom corner. Besides the expression "Pyorrhea Tooth Powder" was written in a distinctive manner in red ink in s