26 READINGS IN BIOLOGICAL SCIENCE 



tered over the body are the rudiments of the uniform hairy coat of the 

 lower animals. This view is rendered all the more probable, as it is known 

 that fine, short, and pale-coloured hairs on the limbs and other parts of the 

 body, occasionally become developed into "thickset, long and rather coarse 

 dark hairs," when abnormally nourished near old-standing inflamed sur- 

 faces. 



The fine wool-like hair, or so-called lanugo, with which the human 

 foetus during the sixth month, is thickly covered, offers a more curious 

 case. It is first developed, during the fifth month, on the eyebrows and 

 face, and especially round the mouth, where it is much longer than that 

 on the head. A moustache of this kind was observed by Eschricht on a 

 female foetus; but this is not so surprising a circumstance as it may at first 

 appear, for the two sexes generally resemble each other in all external char- 

 acters during an early period of growth. The direction and arrangement of 

 the hairs on all parts of the foetal body are the same as in the adult, but are 

 subject to much variability. The whole surface, including even the fore- 

 head and ears, is thus thickly clothed; but it is a significant fact that the 

 palms of the hands and the soles of the feet are quite naked, like the inferior 

 surfaces of all four extremities in most of the lower animals. As this can 

 hardly be an accidental coincidence, the woolly covering of the foetus 

 probably represents the first permanent coat of hair in those mammals 

 which are born hairy. Three or four cases have been recorded of persons 

 born with their whole bodies and faces thickly covered with fine long 

 hairs; and this strange condition is strongly inherited, and is correlated with 

 an abnormal condition of the teeth. Prof. Alex. Brandt informs me that he 

 has compared the hair from the face of a man thus characterised, aged 

 thirty-five, with the lanugo of a foetus, and finds it quite similar in texture; 

 therefore, as he remarks, the case may be attributed to an arrest of develop- 

 ment in the hair, together with its continued growth. 



It appears as if the posterior molar or wisdom-teeth were tending to 

 become rudimentary in the more civilised races of man. These teeth are 

 rather smaller than the other molars, as is likewise the case with the corres- 

 ponding teeth in the chimpanzee and orang; and they have only two sep- 

 arate fangs. They do not cut through the gums till about the seventeenth 

 year, and I have been assured that they are much more liable to decay, and 

 are earlier lost than the other teeth; but this is denied by some eminent 

 dentists. They are also much more liable to vary, both in structure and in 

 the period of their development, than the other teeth. In the Melanian 

 races, on the other hand, the wisdom-teeth are usually furnished with three 

 separate fangs, and are generally sound; they also differ from the other 

 molars in size, less than in the Caucasian races. Prof. Schaaffhausen accounts 

 for this difference between the races by "the posterior dental portion of 

 the jaw being always shortened" in those that are civilised, and this short- 



