STRENGTH OF THE HUMAN JAW.

Manawatu Herald, Volume XXIX, Issue 3777, 9 November 1907, Page 3

STRENGTH OF THE HUMAN JAW.

The crushing power of the hu man jaw is surprising, varying from 150 to 300 pounds. It is also surprising how much jaw strength is exerted unnecessarilj T bj r many persons in eating, often with the result of cracking or breaking the teeth. They crush their food with the ferocity of wild animals. Some experiments recently made by Dr Joseph Head, of Philadelphia, furnish exact figures on this subject, which are as valuable as they are interesting. Weights are given for a large list of foods, and a comparison of the figures should be a valuable guide in selecting the diet of those who are weak for any reason and need to economise their strength, also of those who chew with “store teeth.” The first experiment was made with dry crusts, which broke under 15 pounds pressure. When, however, the combined crusts and soft inside were tried, even 60 pounds pressure would not go through the dense mass. When a little saliva was added a pressure of three pounds was amply sufficient. The deductions with regard to fresh bread and thorough mastication are obvious. People are sometimes greatly surprised at having broken a tooth when they only “ bit a soft crust.” Here are a few figures taken from Dr Head’s tables. Of course, allowance is to be made for the fact that each food, and especially each kind of meat, will vary in reductability according to quality and other conditions. The weight needed to reduce corned beef, with the ihelp of a little grinding movement, was eo pounds; for roast beef, 20 to 35 pounds; tough “round” sirloin, xo to 43 pounds; pork chops, 25 to 30 pounds.

The lowest on the list was boiled beef, three pounds; roast lamb four pounds; tongue, one-half pound. No mention is made of hash. Dr Black states that the human jaw will exert a pressure as high even as 300 pounds.—Popular Mechanics.