48 Proceedings of Indiana Academy of Science 
tapeworms, and round-worms, ascarids, which occur in the digestive 
tract of dogs. The digestive juices were extracted from the pancreas 
of a dog; they were properly activated and kept in containers main- 
tained at the temperature of a dog’s body. Live worms that were 
taken from dogs were unaffected by the fluid, but if worms were added 
after first killing one-half, or one-third or the whole of the body by 
passing a strong electric current through it, only such killed portions 
were digested, the balance remaining active. What could be the as- 
signable reason? To say it occurred ‘because they were alive” was 
not a solution, but when a section of the tubular body of the ascarid, 
which is searcely the diameter of the quill of a chicken feather, was 
slipped over a small porous cup coated with platinum black and «Alled 
with hydrogen peroxide, such dead portion was not digested by the 
digestive fluids. Thus we are led to the conclusion that so long as 
the tissues are saturated with oxygen or that an oxidizing substance 
is available the digestive enzymes are broken down and are rendered 
ineffective. It is believed that the body of the live worms produces 
materials that oxidize the digestive enzymes as effectively as was done 
by the platinum black and the hydrogen peroxide, in the experiment 
that has been quoted. 
The progeny of the intestinal worms are discharged by way of the 
digestive tract of the host, either in the form of eggs that hatch in 
the soil, or only after being eaten by a new host, or they may be in 
an advanced stage of development when they pass out of the host. In 
the moist soil they may live and move with almost the same ease as 
the free-living forms with which they mingle. Here they may remain 
alive for long periods, whether they remain moist or wholly dried, some 
to force their way through the skin into the body of the host and 
finally into the digestive tract, as the hookworms of dogs and cats, or 
of man; others to be taken up by hogs, and after a devious course to 
reach the ‘tigestive tract or lungs and there to become adults and in 
turn to discharge other thousands of eggs. 
If time permitted one might outline, in a similar manner, the 
mode of life and adaptations of the parasitic protozoa, the one- 
celled animals, to show how they also encounter hazards that relate to 
food, temperature and dispersal, to each of which the parasite must 
become adjusted in the period of transition from a free-living state to 
that in which it depends solely upon a host or a series of hosts for its 
existence. 
The problems of life of the successful parasites, whatever their 
kinds, are numerous and critical, but each, in its free-for-all struggle, 
survives if it is resistant, and leaves progeny that resemble it, or it 
fails in the struggle and thus passes out of existence. It has had its 
thousandth of a chance, or a ten-thousandth of a chance or less, and 
failed, while some other competitor, only slightly better fitted for the 
conditions, will survive and perpetuate its heritage. 
Purdue University. 
