ORGANIC DEPENDENCE AND DISEASE 
15 
PROTECTIVE COVERING A BASIC FACTOR 
IN DEPENDENCE 
A knight in armor is a protected fighter and by his pro- 
tection increases his viability. A man “on his own,” who 
fights with his “dukes,” risks his viability but nevertheless 
increases his physical vigor and exalts his bodily prowess. 
A recent writer on the morale of our army in France brings 
out the fact that a man who could defend himself with his 
fists made a better soldier than the one who depended alone 
on the weapon he carried in his hand. 
Nature has given to a large part of the animal world one 
or the other of two solid supports for the soft organs and 
flesh of the body ; an inside skeleton, like that on which our 
own soft anatomy is hung, or an outside skeleton or shell, 
to which we may here give special attention. I have used 
the expression, nature has given , meaning that the neces- 
sity of support to the body having early shown itself, such 
supports developed in response to external impacts and 
internal stresses ; the historical course of development of 
these calcareous supports makes the fact sufficiently obvi- 
ous that they are a determined sequence and not a chemical 
reaction or a casual device. 
A rliizopod, a speck of soft protoplasm with the mar- 
vellous special function of eliminating the silica from its 
solution in the sea, exudes this mineral matter in the 
form of an outside shell of wondrous delicacy and sym- 
metry. The unprotected soft tissue in the primitive ances- 
try of all the great tribe of the Mollusca or sliell-fish, tossed 
haphazard on the sea bottom and hopeless against attack 
except through concealment or powers of rapid self-propul- 
sion, acquires the special function of eliminating from the 
sea the salts of lime, carbonate or phosphate, and with them 
builds up its outside shell. We have just noticed that even 
today the young of such liard-shelled mollusks, in stages 
when their shells are but beginning to grow, are free swim- 
