INTRA-UTERINE INFLUENCES. 293 



even death) in the sucking infant ; " * and it is not 

 unreasonable to suppose that the nutritive fluids may 

 be modified by a similiar influence during the period 

 of gestation. 



Among the abnormal conditions produced by an 

 arrest of development are hare-lip, cleft-palate, fissures 

 of the body or of the spinal column (spina Ufida\ 

 absence or malformation of the limbs, deficient num- 

 ber of the digits, etc. 



The limbs of all vertebrate animals are formed by 

 " a kind of budding process, as offshoots of the exter- 

 nal layer of the blastodermic membrane. They are 

 at first mere rounded elevations, without any separa- 

 tion between the fingers and toes, or any distinction 

 between the different articulations. 



" Subsequently the free extremity of each limb 

 becomes divided into the phalanges of the fingers or 

 toes ; and afterward the articulations of the wrist and 

 ankle, knee and elbow, shoulder and hip, appear suc- 

 cessively from below upward." a 



The feet of frogs, of birds, of squirrels and rab- 

 bits, of cattle, and even the feet and hands of the 

 human foetus, are all, in an early stage of development, 

 webbed as if fitted for swimming, and the characteris- 

 tic form of the digits in each species is only observed 

 at a later period of growth.* 



The divergence from this common type, observed 



1 Dr. A. Combe, on " The Management of Infants," p. 76, quoted 

 in Carpenter's "Human Physiology," p. 1011. 



8 Dalton's " Human Physiology," p. 630. 



3 Agassiz's " Lectures on Embryology," p. 102 ; Carpenter's " Hu- 

 man Physiology," p. 1007 ; Colin, " Physiologic Comparee," etc,, tome 

 ii., p. 570. 



