This trend was driven by cultural changes as well as increased sanitation measures,[89] and it continued throughout the 19th and much of the 20th century, with a notable increase after Elijah Pratt invented and patented the India-rubber nipple in 1845.[2][90] As early as 1846, scientists and nutritionists noted an increase in medical problems and infant mortality was associated with dry nursing.[4][91] In an attempt to improve the quality of manufactured baby foods, in 1867, Justus von Liebig developed the world's first commercial infant formula, Liebig's Soluble Food for Babies.[92] The success of this product quickly gave rise to competitors such as Mellin's Food, Ridge's Food for Infants and Nestlé's Milk.[93]