524 THE POPULAR SCIENCE MONTHLY. 



There exists in the individual organism a duplex relation be- 

 tween growth and structure which it is difficult adequately to express. 

 Excluding the cases of a few low organisms living under special 

 conditions, we may properly say that great growth is not possible 

 without high structure. The whole animal kingdom, throughout its 

 invertebrate and vertebrate types, may be cited in evidence. On the 

 other hand, among the superior organisms, and especially among 

 those leading active lives, there is a marked tendency for completion 

 of structure to go along with the arrest of growth. While an animal 

 of elevated type is growing rapidly, its organs continue imperfectly 

 developed the bones remain partially cartilaginous, the muscles are 

 soft, the brain lacks definiteness ; and the details of structure through- 

 out all parts are finished only after growth has ceased. Why these 

 relations are as we find them, it is not difficult to see. That a young 

 animal may grow, it must digest, circulate blood, breathe, excrete 

 waste products, and so forth ; to do which it must have tolerably-com- 

 plete viscera, vascular system, etc. That it may eventually become 

 able to get its own food, it has to develop gradually the needful appli- 

 ances and aptitudes; to which end it must begin with limbs, and 

 senses, and nervous system, that have considerable degrees of effi- 

 ciency. But, along with every increment of growth achieved by the 

 help of these partially-developed structures, there has to go an altera- 

 tion of the structures themselves. If they were rightly adjusted to the 

 preceding smaller size, they are wrongly adjusted to the succeeding 

 greater size. Hence, they must be remoulded unbuilt and rebuilt. 

 Manifestly, therefore, in proportion as the previous building has been 

 complete, there arises a great obstacle in the shape of unbuilding and 

 rebuilding. The case of the bones shows us how this difficulty is met 

 by a compromise. In the thigh-bone of a boy, for instance, there ex- 

 ists, between the condyle, or head, and the cylindrical part of the bone, 

 a place where the original cartilaginous state continues ; and where, 

 by the addition of new cartilage and new osseous matter, the shaft of 

 the bone is lengthened : the like going on in an answering place at the 

 other end of the shaft. Complete osssification at these two places oc- 

 curs only when the bone has ceased to increase in length ; and, on con- 

 sidering what would have happened had the bone been ossified from 

 end to end before its growth was complete, it will be seen how great 

 an obstacle to growth is thus escaped. What holds here, holds 

 throughout the organism : though structure up to a certain point is re- 

 quisite for further growth, structure beyond that point impedes growth. 

 How necessary is this relation we shall equally perceive in a more com- 

 plex case say, the growth of an entire limb. There is a certain size 

 and proportion of parts, which a limb ordinarily has in relation to the 

 rest of the body. Throw upon that limb extra function, and within 

 moderate limits it will increase in strength and bulk. If the extra 

 function begins early in life, the limb may be raised considerably 



