MARINE SCIENCE TST 
of shellfish. At the present, neither the time nor the reason for the 
toxicity can be predicted ; so for economic as well as for health reasons 
these phenomena should be studied. 
3. Many diseases are caused by parasites. This holds both for man 
and for the animals that he uses for food. Much progress has been 
made in recognizing the symptoms of parasitism, but very little in 
understanding the underlying reasons for it. Among marine animals 
there are whole series of closely related forms, each showing different 
degrees of dependency or susceptibility to parasitism. There are also 
whole phyla in me parasitism is unknown; others in which it is 
the rule. Study of these animals, especially those where parasitism 
exists in its simplst or most primitive expression, will teach us much 
about the basic causes of the parasitic mode of life. 
Bacterial diseases similar to or identical to tuberculosis and leprosy 
infect important food fishes such as salmon, yet other fishes and other 
marine animals in the same water environment are apparently im- 
mune to these diseases. Why this is so, no one knows. More 
knowledge of how the salmon are infected, whether the disease can be 
transmitted, and why other marine animals are immune, is badly 
needed. For some disease-causing bacteria sea water has apparently 
a sterilizing effect; conversely certain types wounds—e.g., scratches 
from corals, barnacles, sea urchin spines—are very apt to become 
infected. Reasons for this also are unknown. 
4, Progress in medical science depends in large part upon progress 
in the knowledge of normal physiological functions. Unless the nor- 
mal living animal is understood, the variations that we call ill-health 
or disease are meaningless perplexities. Obviously man can seldom 
experiment upon himself, but most physiological processes are basi- 
cally similar throughout the animal kingdom and the study of other 
animals contributes importantly to knowledge that in turn contributes 
to human health and welfare. 
_ Because they represent the greatest diversity from simple to com- 
plex, and because they show myriad variations both anatomically 
and functionally, marine animals provide essential information in 
many physiological studies. ; 
We have already mentioned how understanding neurological phe- 
nomena have been clarified by the squid and other mollusks; at 
present there are experiments on the brain of octopus that are helping 
to elucidate the nature of learning and of mental disorders; from 
crabs and shrimps come substances that mhibit nerve impulses; 1m 
heart research lobsters, clams, and worms are adding their bit to the 
store of knowledge, for their cardiac responses are different from 
those of vertebrates. 
One of the most active fields of medical research today involves 
studies of tissue compatability and the nature of immunity. Here 
animals we call sponges are especially useful experimental material 
for their tissues can be separated into the constituent cells that then 
are capable of reaggregating to form the typical animal once more. 
The eggs and embryos of marine invertebrates also contribute to this 
field. Their study is even more important in learning about the 
factors that stimulate cell division and control its rate—information 
that is basic to unravelling some of the perplexities surrounding the 
growth of cancer and neoplasms. 
