If the femur belongs with the skull, the Trinils were a tall race, reaching a height of 5 feet 7 inches as compared with 5 feet 3 inches in the Neanderthals. The thigh-bone (Fig. 122) has a very slight curvature as compared with that of any of the apes or lemurs, and in this respect is more human; it is remarkably elongate (455 mm.), surpassing that of the Neanderthals; the shin-bone (tibia) was probably correspondingly short. The two upper grinding-teeth preserved are much more human than those of the gibbon, but they do not resemble those of man closely enough to positively confirm the prehuman theory. Dubois observes:(25) "That the tooth belongs to some hominid form needs no further demonstration. Aside from its size and the greater roughness of the grinding surface, it differs from the human grinder in that the less developed cusp of _Pithecanthropus_ is the posterior cusp next the cheek, while in man it is generally the posterior cusp next the tongue. The simplification of the crown and the root of the Trinil grinder is quite as extensive as it usually is in man." [Illustration: FIG. 38. Profile view of the head of _Pithecanthropus_, the Java ape-man, after a model by J. H. McGregor. One-quarter life size.] Various efforts have been made to supplement the scattered and scanty materials collected by Dubois. The Selenka expedition of 1907-8 brought back a human left lower molar as the only result of an express search for more _Pithecanthropus_ remains. Dubois is also said to possess the fragment of a primitive-looking lower jaw from the range known as the Kendeng Hills, at the southern base of which lies the village of Trinil. It remains for us to consider the stage of psychic evolution attained by the Trinil race, and this naturally turns upon the erect attitude and what little is known of the size and proportions of the brain. [Illustration: FIG. 39. Front view of the head of _Pithecanthropus_, the Java ape-man, after a model by J. H. McGregor. One-quarter life size.] The assumption of the erect attitude is not merely a question of learning to balance the body on the hinder extremities.(26) It involves changes in the interior of the body, the loss of the tail, the freeing of the arms, and the establishment of the diaphragm as the chief muscle of respiration. The thigh-bone of _Pithecanthropus_ is so much like that of man as to support the theory that the erect position may have been assumed by the ancestors of man as early as Oligocene times. It would appear that _Pithecanthropus_ had free use of the arms and it is possible that the control of the thumb and fingers had been cultivated, perhaps in the fashioning of primitive implements of wood and stone. The discovery of the use of wood as an implement and weapon probably preceded that of the use of stone.