One of the oldest and most important of these are the kidneys or nephridia, which removeunusable matter from the body (Figure 2.
They can absorb either solid or dissolved particles from the wall of the gut, and convey them to the blood in the chyle; they can absorb and remove unusable matter from the tissues.
They act for a time as kidneys, absorbing unusable juices from the embryonic body and conducting them to the cloaca--afterwards to the allantois.
A small trace will not make much difference, but some waters contain a great deal of iron, so much so that they are absolutely unusable for bleaching purposes.
Of course sooner or later the baths become unusable from various causes, and then they may be thrown away; but old tannin baths often work better than the new ones.
But even in the quantities which have already appeared on the battle-field, it has rendered whole zones practically unusable for huge masses of men, owing to the certainty of a very high percentage of casualties.
The number of propositions remains substantially the same as in Euclid, and the introduction of some unusable logic tends to counterbalance the improvement in sequence of the propositions.
