374 ANIMAL PHYSIOLOGY. 
Personal Observation. The student would do well at this stage 
to test the statements we have made in regard to the respira- 
tory movements on the human subject especially. This he 
can very well do in his own person when stripped to the waist 
before a mirror. Many of the abnormalities of the forced res- 
piration of disease may be imitated—in fact, this is one of the 
departments of physiology in which the human aspects may 
be examined into by a species of experiment on one’s self that 
is as simple as it is valuable. 
Fig. 305.—Protula dysteri, a marine annelid living in a calcareous tube constructed by itself 
(after Huxley). The cut represents the sexually mature animal (hermaphrodite) extracted 
from its calcareous tube. a, branchial (respiratory) plumes, abundantly vascular; b, 
hood-like expansion of anterior end of body ; c, mouth; d, stomach ; e, anus; /, testes; 
g, ova. 
