368 



The Journal of Heredity 



of subsistence. This is indicated by 

 the very speciahzed systems of agri- 

 culture that were developed, as well 

 as by the precautions that the Incas 

 are reported to have taken against 

 famines, which are confirmed by the 



discovery of many ancient storehouses. 

 With the ancient precautions neglected, 

 many districts that were terraced with 

 stone-work, and no doubt were culti- 

 vated very intensely in ancient times, 

 have been abandoned. 



The Diseases of Children 



Saeuglingskrankheiten, by Dr. 

 Walter Birk, Vorstand d. Univ.- 

 KinderkHnik zu Tuebingen. 5. und 6. 

 umgearbeitete Auflage, 10-17 Tau- 

 send. Pp. 283, with 26 illustrations. 

 Price $1.40. Bonn, 1922, A. Marcus 

 & E. Webers Verlag. 



Dr. Birk presents a clear, compre- 

 hensive and well-organized discussion 

 of the diseases of infancy in this vol- 

 ume, which forms part I of his "Leit- 

 faden der Kinderheilkunde," a second 

 volume being given over to "Kinder- 

 krankheiten." He fully recognizes 

 the importance of heredity in the 

 varied problems which the pediatrist 

 meets, although he does not go into 

 this side of the case as fully as some 

 might desire. Speaking of twins, he 

 remarks that thev have the most 



divergent constitutions, in spite of the 

 identity of their surroundings. As to 

 rickets, he declares that eighty per cent 

 of the children in Germany are effected 

 at one time or another, and that in- 

 born predisposition plays an important 

 part. The current theory that rickets 

 is due to lack of vitamines he dis- 

 misses as not in accord with the clin- 

 ical facts. He notes that the negroes 

 in Africa are free from this disease, 

 while it is extremely prevalent among 

 the negroes of North America. The 

 importance of rickets in forming the 

 shape of the female pelvis is often not 

 recognized until the girl becomes a 

 mother. It is in this way of first-rate 

 importance to eugenics. Dr. Birk 

 closes with a brief review of the infant 

 welfare movement. P. P. 



Origin of Mongolian Idiocy 



Mongolian idiocy is a typical form 

 of amentia, taking its name from the 

 fact that the children born with this 

 condition often have a facial expressiin 

 resembling that of the Mongolian race. 

 Its cause is obscure, but has been set 

 down by various writers as "uterine 

 exhaustion," since the last child in 

 large families seems to be more often 

 affected than others. Statistics on the 

 subject have been fragmentary, how- 

 ever. Available data have been re- 

 worked by Hornell Hart, who contrib- 

 utes a note to the Journal of the Amer- 

 ican Statistical Association, XVIII : 



900-903, September, 1923. He finds 

 that a Mongolian anient is twenty- 

 three times as likely to be born to a 

 mother forty ^'Cars old or over, as to 

 a mother between the ages of twenty 

 and twenty-four. It is therefore clear 

 that the condition is correlated with the 

 mother's age ; but the data are not 

 sufficient to show whether the mother's 

 age is significant because of a possible 

 deterioration in the quality of the 

 germ-plasm, or merely because the 

 older mothers are likely to have had 

 more children ; or for some other rea- 



