A PRELIMINARY STUDY OF THE DIGESTIVE SECRE¬ 
TIONS OF PICKEREL AND PERCH 
CAROLINE WALKER MUNRO 
Apparently very little experimental work on the digestive secre¬ 
tions of fish has been done up to this time. That the stomach of 
a fish contains some other acid than hydrochloric (Stewart, 1905), 
and that the secretion of definite enzymes is not limited to fixed 
regions of the alimentary canal as in the mammals (Bridge, 
1910), is known, but what the composition of the enzymes is, or 
what foods the secretions of the different regions of the alimen¬ 
tary canal are adapted to digest, are questions that have appar¬ 
ently had little attention. The purpose of this paper is to state 
the results of a few experiments performed with extracts of the 
digestive juices of perch and pickerel, in an attempt to determine 
which enzymes are adapted to digesting specific classes of foods. 
The experiments were performed in accordance with suggestions 
contained in Stewart’s (1905) Manual of Physiology, which out¬ 
lines methods of determining the digestive action of mammalian 
enzymes, and a comparison was made of the relative strength of 
prepared solutions of panereatin and pepsin with that of fish 
enzymes. A number of preliminary experiments were carried out 
on the digestive secretions of perch. After this two series of 
parallel experiments were made on the enzymes obtained from 
pickerel and perch, as compared with commercial solutions of the 
corresponding mammalian enzymes. 
Pickerel 1 
The extracts of the enzymes were obtained from a pickerel 
weighing 10.3 pounds, which was found to contain a partially 
digested perch about 6 inches long in its stomach. The mucous 
membranee of the stomach was stripped off, triturated in a mor- 
1 Esox lucius Linnaeus. 
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