The Birmingham age-herald., 1910-10-24
GREAT ENERGY
 OF OUR JAWS Experiments Show Amount of Pressure Exerted in Eating A STUPENDOUS FORGE Is Expended in Talking and in Masti- eating Food-Inyestigation Con-
 ducted in Furthernnce of
 Scientific Dentistry
\ sTUPENDoUs FORGE
.om the New York Tribune.

 to bite the bread that mother makes? An absurd question, you reply. But 1T you think you can thrust your teeth through the particles of fluffy wheat bread you make one of the greatest mistakes or your life Such is one of the latest dls- coveries of science, announced as re- suit of a series of tests made to deter mine the amount of pressure exerted by the human jaw In the process of masti- eating food.
 Do you know that the woman who par ticipates In the ordinary conversation or the gossipfest shuts her jaws together with force of 60 pounds every time she utters a syllable, while man in vehe- ment oratory make teeth crash against teeth with 100-pound blows?
 pr. Greene Vardiman Black Is the man who does know He Is the dean or North western universitys dental school in Chi cago For r years he has been testing the strength of the muscles of the human jaw to ascertain how hard men and wom- en bite. Of late he has directed his ex- periments to the number of pounds pres sure exerted by the lower jaw In the mastication of different kinds of food.
 strhe Pressure Registered
 The earlier experiments were carried on bv means of the thodynamometer which pr. Black invented. This re- sembles a pair of pliers about live inches long. The jaws of the device are held open by apparatus similar to that of spring scale. which Is lncloseo between what might be termed the han dies of the pliers. To this apparatus IS attached a pointer that registers the
 
 the jaws of the instrument In closing or partly closing them. The test with this instrument is simple. The subject opens his mouth half to three-quarters of an inch enough to admit the inser- ton of the jaws between his teeth, then bites as hard as he can on the jaws or the gnathodynamometer, which are cov- cred with hard rubber for the protec- ton of the teeth The pointer denotes the number of pounds pressure ex- erted, just as pair of scales indicates the weight of a pound of sugar at the custom house since the government in vestigation began there.
 Results Astonishing
 With a class of six students Professor Black obtained results showing wide diff ferences in the power of the muscles to close the human jaws. One student reg istered 150 pounds pressure, another 155, a third 190, the fourth 220 the fifth 225, and the sixth 250 pounds. In tests with other classes there were subjects whose maximum pressure was as low as 100 and as high as 300 pounds. One student brought the jaws of the gnathodynamo- meter together with a snap repeatedly. The instrument he used, the only one available at the time, had maximum capacity of 275 pounds. The ease and -rapidity with which he closed it con- vinced Professor Black that his jaw muscles were capable of at least $50 pounds pressure.
 All these tests and many others of the same kind had a specific object relating to the construction of false teeth and the filling of natural ones. In fact it was in furtherance of the scientific practice of dentistry that Dr. Black investigated. the subject at all, and the same purpose led him on to the study of the pressure of the jaws in the processes of mastication and conversation.
 Impossible to Bite Bread
 Bread, says Professor Black, is the most difficult and damaging food the teeth have to contend with. Even with pressure of 300 pounds, 1t Is impossible to bite bread In attempts to bite bread the teeth are often broken. Its masti- cation is made possible only by reason of the fact that the jaws of man are so fashioned that the teeth come together with a grinding motion. There Is a sci- entific reason, then, for breaking bread into small pieces with the fingers be- fore attempting to grind it In mastication. Even then all the strength of the jaw muscles, whether capable of 50 or 800 pounds pressure, will be put forth in mastering it.
 To obtain definite results he invented the hagodynamometer, or chewing ma chine. In general way this is like the gnathodynamometer, but is more intri- cate. It is designed to record the pres sure employed in eating without inter fering with the natural motion of the under jaw.
 The tests with the phagodynamometer brought forcibly to the attention of sci- entists the fact that many persons do not really mastigate their food at all. Some of the subjects produced records of only 50 pounds pressure. Such persons, says Dr. Black, merely pat their food into bolus with their teeth and swallow If without chewing it."