THE CATALASE CONTENT OF ASCARIS SUUM,* WITH A 
SUGGESTION AS TO ITS ROLE IN PROTECTING 
PARASITES AGAINST THE DIGESTIVE 
ENZYMES OF THEIR HOSTS. 
By THOMAS BYRD MAGATH. 
(From the Department of Anatomy, College of Medicine, University of Illinois, 
Chicago.) 
(Received for publication, January 8, 1918.) 
Many explanations have been offered as to why gastric and intestinal 
parasites are not digested by their hosts. A brief survey and discussion 
of many theories can be found in text-books on physiology, for this ques- 
tion resolves itself into the time-worn query, Why is living tissue not 
digested? The theory which has perhaps gained most attention is that 
anliferments or antienzymes protect living matter, and this theory has 
been used by Weinland (1903) to explain the resistance of intestinal para- 
sites to the destructive influence of digestive enzymes. Upon rubbing up 
Ascaris into a pulp and extracting with alcohol he obtained a substance 
which he termed Antifermente because he claimed that this substance 
protected the proteins from the proteolytic action of pepsin and trypsin. 
On the basis of his own interpretation this theory was open to criticism 
because he had to kill the worms to obtain the substance, and it was argued 
that if the antiferment existed after death it should protect the dead worms 
as well as the living. More recent work on the antienzymes has offered 
very good explanations for these phenomena, but it is not the intention 
to discuss these intricate facts. 
In recent times Burge and Burge (1915, a) have advanced another 
theory which might be termed an ‘“‘oxidation theory,’’ and they have 
used this not only to explain the resistance of intestinal parasites to the 
digestive action of their hosts, but maintain that living cells protect them- 
selves from the destructive enzymes by means of the oxidation processes 
going on in them. It has been shown that the mucosa of the stomach 
and intestines possesses intense oxidative propertiés, and Burge (1914) has 
shown that the digestive enzymes are very easy to oxidize and are then in- 
active. By applying these facts to intestinal parasites he was able to 
demonstrate that living worms are not digested while dead worms are, 
and if the dead ones are permeated with nascent oxygen they withstand 
*Tt is not unlikely that Ascaris swum and Ascaris lumbricoides are 
identical. 
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