CARTILAGE AND CONNECTIVE TISSUE. 107 



the tissues concerned, and it is nearly as bad to wheel a child 

 about forever in a baby-carriage as to force it to over exertion. 



The best rule is to let a healthy child use its limbs when 

 it feels "inclined, but not by praise or blame to incite it to 

 efforts which are beyond its age, and so sacrifice its healthy 

 growth to the vanity of parent or nurse. 



The final knitting together of the bony articular ends 

 with the shaft of many bones takes place only comparatively 

 late in life, and the age at which it occurs varies much in 

 different bones. Generally speaking, a layer of cartilage re- 

 mains between the shaft and the ends of the bone, until the 

 latter has attained its full adult length. To take a few 

 examples : the lower articular extremity of the humerus 

 only becomes continuous with the shaft by bony tissue in the 

 sixteenth or seventeenth year of life. The upper articular 

 extremity only joins the shaft by bony continuity in the 

 twentieth year. The upper end of the femur joins the shaft 

 by bone from the seventeenth to the nineteenth year, and 

 the lower end during the twentieth. In the tibia the upper 

 extremity and the shaft unite in the twenty-first year, and 

 the lower end and the shaft in the eighteenth or nineteenth : 

 while in the fibula the upper end joins the shaft in the 

 twenty-fourth year, and the lower end in the twenty-first. 

 The separate vertebras of the sacrum are only united to form 

 one bone in the twenty-fifth year of life; and the ilium, 

 ischium, and pubis unite to form the os innominatum about 

 the same period. Up to about twenty-five then the skeleton 

 is not firmly "knit," and is incapable, without risk of injury, 

 of bearing strains which it might afterwards meet with im- 

 punity. To let lads of sixteen or seventeen row and take 

 other exercise in plenty is one thing, and a good one; but to 

 allow them to undergo the severe and prolonged strain of 

 training for and rowing a long race is quite another, and not 

 devoid of risk. 



Adipose Tissue. Fatty substances of several kinds exist 

 in considerable quantity in the Human Body in health, some 

 as minute droplets floating in the bodily liquids or imbedded 

 in various cells, but most in special cells, nearly filled with 

 fat, and collected into masses with supporting and nutritive 

 parts to form adipose tissue. In fact almost in every spot 

 where the widely distributed areolar tissue is found, there is 

 adipose tissue in greater or less proportion mixed with it. 



