174 STRUCTURE OF THE VERTEBRATES 



nutrition and otlier environmental factors also influence height, 

 particularly in species which have a definite size limit. Those 

 which continue growth throughout life are less influenced by 

 periods of semi-starvation. Malformations of bone may be due 

 to injuries of the periosteum, or to improper feeding. Rickets, 

 which causes bowed legs and other deformities, is caused by a 

 lack of bone developing vitamines. There are, however, racial 

 and individual differences in susceptibility to the condition. 



