146 ANIMAL PHYSIOLOGY. 
tions, so precisely defined as to meet the demands of science, 
may be made by the intelligent student. Much of this might 
be verified in the case of other healthy persons. Some of it is 
in certain respects of more value than any experiments that 
can be made upon the lower animals, for the latter can not 
communicate to us their sensations; in their case all our in- 
formation must be derived from the use of our own senses, 
mostly unaided by any reports of theirs. 
It is not possible during any experiment, especially any one 
in which vivisection is employed, to observe the animal under 
conditions that are strictly normal, for, by the very nature of 
the case, we have rendered it abnormal. We must in all such 
instances draw conclusions with corresponding caution. It 
will be understood that the expression “conclusive experi- 
ment,” as applied to such a case, is only approximately correct. 
At the present time it is very common to experiment upon 
organs disconnected, either anatomically or physiologically 
(functionally), from the rest of the body to a greater or less 
extent. This is termed the isolated method. It has the advan- 
tage of being more simple, and permits of the study of certain 
points apart from others—one factor being considered inde- 
pendently of the rest in the physiological total. But, in draw- 
ing conclusions, it is very important in such a case not to forget 
the premises. There is manifest danger of making the gener- 
alization wider than the facts warrant. It is only when such 
experiments are supplemented by a great many others, and 
when judged in connection with the action of the organ under 
consideration, as it is influenced by other organs, that such re- 
sults can be of great value in building up a normal physiology. 
To know, for example, that the isolated heart behaves in a cer- 
tain manner is not useless information, but its value depends 
entirely on the conclusions drawn from it, especially as to what 
it is conceived as teaching of the functions of the heart as it 
beats within the body of an animal while it walks, or flies, or 
swims, in carrying out the purpose of its being. 
We have incidentally alluded to the teaching of disease. 
“Disease” is but a name for disordered function. One viewing 
a piece of machinery for the first time in improper action might 
draw conclusions with comparative safety, provided he had a 
knowledge of the correct action of stmilar machines. Our ex- 
perience gives us a certain knowledge of the functions of our 
own bodies. By ordinary observation and by experiment on 
other animals we get additional data, which, taken with the 
