8 PREFACE. 
which the instruments should be held, etc., or to point 
out all the numerous possible mistakes which may be 
made. It is better to leave something to the intelli- 
gence and discretion of the teacher or the pupil, if the 
dissecting is to prove a healthy discipline. 
It is but proper to say that the general idea of the 
arrangement of the directions for dissection was taken 
from the very excellent book on “ Practical Zoology ” 
by Marshall and Hurst. 
I take pleasure also in expressing my thanks to my 
friend Mr. T. D. Coleman, Assistant in Physiology in 
this laboratory, for his kindness in helping me in the 
dissections and in the preparation of the diagrams. 
W. H. Howe ut. 
Jouns Hopkins UNIVERSITY, 
BALTIMORE, Mp. 
