From “Report of the Commissioner for the year ending June 30, 1902 : Aquatic products in arts and industries : fish oils, fats, and waxes. Fertilizer from aquatic products” / by Charles H. Stevenson, (page 197).
“The term ‘twitter,’ which has been previously referred to as applied to the thread-like or membranous substance ranging through the contents of the case, is also applied to the lining of that reservior. This is from 2 to 3 inches thick, glutinous, and extremely tough. In decapitating the sperm whale, especially in severing near the bunch of the neck, a very sharp spade is required to cut through this tough and elastic formation. Although it is very difficult to manipulate, an economical whaleman never throws this substance away. Since it can not be boiled out with the case, for the reason above given, it is saved and run through the pots with the fat-lean after the case and junk have been cooked.”
Research by Maritime Curator Mike Dyer (firstname.lastname@example.org):