THE ANATOMY OF THE HEART OF CAMBARUS. 
W. S. MILLER, M. D. 
Instructor in Vertebrate Anatomy, University of Wisconsin. 
WITH PLATES Y AND VI. 
The discrepancy that exists between the heart of the Cray¬ 
fish, as usually described, and the actual condition as found by 
dissection, led me to make a careful study of the heart of our 
common Crayfish. In the carrying out of this work Mr. J. D. 
Madison, one of my students, gave me very material assistance, 
the mechanical part of the work being done by him. 
It will be found on looking over the literature of the subject, 
that in nearly every instance in which a description of the heart 
of the Crayfish is given, it is taken directly from Huxley’s 
work, or it is based on his description. 1 The form used by 
Huxley was Astacus, and although I have not had an opportunity 
to verify his results, I presume them to be correct. The com¬ 
mon Crayfish with us is not Astacus but Cambarus. Huxley 
noted several points of distinction between the two forms, men¬ 
tioning especially the reduction in the number of gills. As the 
result of my study, I have found that Huxley’s account of the 
heart of Astacus can not be applied to that of Cambarus. 
If a portion of the carapace of a live Crayfish be carefully re¬ 
moved from the mid-dorsal region, there is exposed to view a 
place where a regular pulsation may be seen; this marks the 
situation of the heart. Continuing the dissection of the tissues 
underlying the carapace, there is brought into view a cavity 
irregularly quadrangular in shape; occupying a considerable 
portion of this cavity will be seen a fleshy mass, much the same 
shape as the cavity but smaller, which contracts and dilates 
with a constant regularity. The cavity is usually called the 
Anatomy of Invertebrated Animals, 1878. 
An Introduction to the Study of Zoology, Illustrated by the C rayfish, 
1879. 
