494 POPULAR SCIENCE MONTHLY 



the brain is due in part to the shrinkage of the single microscopic con- 

 stituents. There is another point of resemblance. We find that when 

 one of the better parts of the body undergoes an atrophy, it becomes 

 not only smaller, but its place is to a certain extent taken by the in- 

 ferior tissues — especially by those which we call comprehensively the 

 connective tissues, which might perhaps be best described to a general 

 audience as that which is the stuffing of the body and fills out all the 

 gaps between the organs proper. In consequence of performing this 

 general function, they are very properly called connective tissues, 

 since they connect all the different organs and systems of organs in 

 the body together. Now in every body there is a continual fighting 

 of the parts. They battle together, they struggle, each one to get 

 ahead, but the nobler organ, generally speaking, holds its own. There 

 are early produced from the brain the fine bundles of fibers which we 

 call the nerves, which run to the nose, to the tongue and to the various 

 parts of the body. When these appear all the parts of the body are 

 very soft. Afterwards comes in the hard, and, we should think, sturdy 

 bone, but never, under normal conditions, does the bone grow where 

 the nerve is. The nerve, soft and pulpy as it seems, resists absolutely 

 the encroachment of the bone, and though the bone may grow else- 

 where, and will grow elsewhere the moment it gets a free opportunity, 

 it can not beat the soft delicate nerve. 6 Similarly we find that the 

 substance which forms the liver is pulpy, very delicate. Those of 

 you who have seen fresh liver in the butcher's shop know what a flabby 

 organ it is, and yet though it is surrounded by the elements of con- 

 nective tissue, which with great zest and eagerness produce tough 

 fibers, it never gives way to them. The connective tissue is held 

 back by the soft liver and kept in place by it. The liver is, so to speak, 

 a nobler organ than the connective tissue and holds sway ordinarily; 

 but in old age, when the nobler organs lose something of their power, 

 then the connective tissue gets its chance, grows forward and fills 

 up the desired place, and acquires more and more a dominating posi- 

 tion. We can see this alike in the brain of man and in the brain of 

 the bee. That which is the nervous material proper, microscopic ex- 

 amination shows us to be diminished everywhere in the old bee and in 

 the old man, and the tissue which supports it, which is of a coarser 

 nature and can not perform any of the nobler functions, fills up all 

 the space thus left, so that the actual composition of the brain is by 

 this means changed. There is, you see, therefore, during the atrophy 



8 The nerve fibers of the olfactory membrane arise very early in the embryo 

 and form numerous separate bundles. Later the bone arises between the bundles, 

 for each of which a hole is left in the osseous tissue, so that the bone in the 

 adult has a sieve-like structure, and hence is termed the cribriform plate. It 

 offers a striking illustration of the inability of hard bone to disturb soft 

 nerve fibers. 



