,314 



THE ANIMAL KINGDOM. 



they are connected to the bones which they sometimes serve 

 to prolong, and are themselves often converted into bone 

 in old people, by the deposition of earthy matter within 



PIG. 79. INVOLUNTARY MUSCULAR FIBRE. 



their structure, in fact, they may be considered as bone 

 in an undeveloped state ; for, in the infant, many parts are 

 cartilaginous, which, in the adult, are bony; such as the 

 ..ends of the long bones, the bones of the nose, &c. 



With respect to the development of the form of the 

 human body, there are two chief conditions which influence 



FIG. 80. HEAD OF AS INFANT. 



it, namely, age and sex. With respect to age, the propor- 

 tional magnitudes of the different parts, early and late in 



