Complex sentence: He was feeding the cats a supposedly nutritive diet (according to the experts of his day) consisting of raw milk, cod liver oil and cooked meat scraps of liver, tripe, sweetbread, brains, heart and muscle.
Split into simpler sentences: He was feeding the cats a supposedly nutritive diet according to the experts of his day. The diet consisted of raw milk, cod liver oil and cooked meat scraps of liver, tripe, sweetbread, brains, heart and muscle.