THE ASCENT OF MAN. 463 



near mau as a formidable weapon of defense. The shortening has 

 produced some very remarkable changes. It has shoved the third 

 molar or " wisdom tooth" so far back that it is crowded against the as- 

 cending part of the jaw, thereby occasioning disturbance and trouble 

 in its eruption. Being no longer practically useful, it tends to dis- 

 appear, and many people never cut any wisdom teeth. Among tbe 

 Australasians, on the contrary, a fourth molar is not iufrefpiently found ; 

 this rarely occurs in European skulls also. Evidences exist of a lost 

 incisor in the upper jaw on each side. Dental follicles form for it and 

 usually abort, but occjisionally the tooth appears fully developed in the 

 adult. The great canines or eye-teeth, used in apes and other animals 

 for tearing and holding, are in them longer and larger than the other 

 teeth, and room is made for them in the opposite jaw by leaving an 

 interval, called the diastema, between the canine and the tooth next to 

 it. These large projecting canines have disappeared in the normal 

 human skull and the diastema has accordingly closed up. Yet it is by 

 no means uncommon to see the whole arrangement re-appear, especially 

 in low type skulls. Projecting canines or " snag teeth" are so common 

 in low faces as to be universally remarked, and would be oftener seen 

 did not dentists interfere and remove them. It maybe noted also that 

 the muscle that lifts the lip from over the canines and bares the weapon, 

 often re-appears in man and is used to produce snarling and disdainful 

 expressions. 



Many details of structure of the skull point in the same direction. 

 Occasionally the occipital bone has a third condyle, as in some other 

 mammals, or a large lateral projection like that of a vertebra, the para- 

 mastoid process, or indications of a separate centrum (o,s hasioticum of 

 Albrecht). It may have interiorly a hollow ( fosseite vermienne) for the 

 vermiform process of the cerebellum, and exteriorly a large transverse 

 ridge {torus occipitalis) on which are inserted tlie muscles of the nape. 

 All these pe(;uliarities are more frequent as we descend the scale, 

 whether we regard the lower races of man, microcephalic individuals, 

 or lower animals. Like many of these atavistic features they are also 

 more common among the criminal classes. 



I have omitted the discussion of many important structural features 

 that mark various stadia in man's ascent. From the muscular system 

 alone there could be adduced a very great number of instances of the 

 survival of primitive forms and of progressive variations, particularly 

 in the development of the mus<;les of the face and breast. In the 

 osseous system also there are many such, among which may be men- 

 tioned the episternal bones, the central bones of the wrist and aidcle, 

 and the os acetahnli. The exact significance of these is st'll under 

 discussion, as is also the question of supernumerary digits that some- 

 times appear on the hands and feet. 



Additional instances might be drawn from the visceral system. The 

 larynx contains small throat pouches like the great air sacs of the 



