104 ANIMAL LIFE 
tatoria and of others called Tardigrada, or bear-animalcules. 
These bear-animalcules live in water. If the water dries 
up, the animalcules dry up too; they shrivel up into form- 
less little masses and become desiccated. They are thus 
simply dried-up bits of organic matter; they are organic 
dust. Now, if after a long time—years even—one of these 
organic dust particles, one of these dried-up bear-animal- 
cules is put into water, a strange thing happens. The body 
swells and stretches out, the skin becomes smooth instead 
of all wrinkled and folded, and the legs appear in normal 
shape. The body is again as it was years before, and after 
a quarter of an hour to several hours (depending on the 
length of time the animal has lain dormant and dried) slow 
movements of the body parts begin, and soon the animal- 
cule crawls about, begins again its life where it had been 
interrupted. Various other small animals, such as vinegar 
eels and certain Protozoa, show similar powers. Certainly 
here is an interesting problem in life and death. 
When death comes to one of the animals with which 
we are familiar, we are accustomed to think of its coming 
to the whole body at some exact moment of time. As we 
stand beside a pet which has been fatally injured, we wait 
until suddenly we say, “It is dead.” Asa matter of fact, 
it is difficult to say when death occurs. Long after the 
heart ceases to beat, other organs of the body are alive— 
that is, are able to pertorm their special functions. The 
muscles can contract for minutes or hours (for a short time 
in warm-blooded, for a long time in cold-blooded animals) 
after the animal ceases to breathe and its heart to beat. 
Even longer live certain cells of the body, especially the 
amoeboid white blood-corpuscles. These cells, very like 
the Ameba in character, live for days after the animal is, 
as we say, dead. The cells which line the tracheal tube 
leading to the lungs bear cilia or fine hairs which they 
wave back and forth. They continue this movement for 
days after the heart has ceased beating, Among cold: 
