INTRA-UTERINE INFLUENCES. 291 



derived that monstrosities do not take place by chance, 

 and therefore do not by any means deserve the so very 

 general appellation of caprices of Nature (lusus no- 

 turoB). The result of this is, that they often present 

 a quantitative antithesis, according to what Geoffroy 

 St.-Hilaire denominates loi de fialancement. 1 Accord- 

 ing to this law the excessive development of one part 

 of the body is often connected with checked forma- 

 tion of another. To anencephalia? cydopia, spina 

 bifida? are often joined fingers and toes in excessive 

 numbers ; to sireno-melia* superfluous vertebrae and 

 ribs ; and frequently there occur in double monsters 

 malformations of the head. Meckel saw in one in- 

 stance this antithesis extend itself over different chil- 

 dren of one and the same mother. A girl had on 

 each extremity a superfluous digit ; one hand of her 

 sister wanted four fingers, being the number of digits 

 which her sister had in excess, reckoning the four 

 extremities together." 6 



The laws of embryological development furnish a 

 satisfactory explanation of the cases in which there is 

 a fancied resemblance of the foetus to some of the 

 lower animals. 



There is a close correspondence between the em- 

 bryos of all vertebrate animals in the earliest stages of 

 development ; " and it is only with the advance of the 

 developmental process that indications successively 



1 Another name for law of correlation. 

 8 Brainless monsters. 



3 Fissure of the spinal column. 



4 Monsters without feet. 



6 W. Vrolik, " Cyclopaedia of Anatomy and Physiology," article 

 " Tetratology," vol. iv., pp. 945, 946. 



