Munro—Digestive Secretions of Pickerel and Perch. 273 
juices of animals living on vegetable matter. The perch, on the 
other hand, which is a versatile feeder (Pearse, 1915), is pro¬ 
vided with an enzyme which to a small extent inverts sugars. The 
enzymes of the pickerel, however, are highly adapted to the thor¬ 
ough digestion of proteins, as evidenced by the fact that the ex¬ 
tracts of the stomach and intestine of the pickerel acted more 
rapidly than a comparable enzyme from mammalian digestive 
glands. 
It appears, moreover, that the perch, in which a pancreas is 
lacking, is provided with active enzymes in the intestine which 
perform the functions ordinarily performed by the pancreas in 
forms possessing that gland. The pancreas of the pickerel does 
not appear from these experiments to be active in digestion, since 
no action was obtained from the use of an extract of it. 
It may be concluded, therefore, that the digestive secretions of 
the fish studied are correlated with their food habits, and that the 
lack of a digestive gland (the pancreas) found in higher verte¬ 
brates, or the non-functional state of that gland if present, are 
compensated for by activity on the part of other digestive glands 
present. 
Zoological Laboratories, 
University of Wisconsin 
Bibliography 
Bridge, T. W. 1910. Fishes. Cambridge Natural History 7: 141- 
537. London. 
Howell, W. H. 1912. A textbook of physiology. 1018 pp. Phila¬ 
delphia and London. 
Pearse, A. S. 1915. The food of the shore fishes of certain Wiscon¬ 
sin lakes. !U. S. Bureau Fisheries, Bull. 25: 249-290. Wash¬ 
ington. 
Pratt, H. S. 1905. A course in vertebrate zoology. 299 pp. Bos¬ 
ton. 
Stewart, G. N. 1905. Manual of physiology with practical exercises. 
911 pp. London. 
18—S. A. L. 
