1893.] Physiology and Morphology. 805 
organic machine and thus lays the foundation for understand- 
ing its physiological use; physiology puts the suggestions of 
morphology to the test of experiment, and elucidates the 
dynamical side of the machine. ^ What the machine consists 
of and what it ean do, go together to make up a full concept 
of its structure and its functions. But the concurrence of the 
two sciences does not stop here. Morphology raises the ques- 
tion, how came the organic mechanism into existence? Has 
it had a history, reaching its present state of perfection 
through a long series of gradations, the first term of which 
was a relatively simple stage? The embryological history is 
traced out and the paleontological records are searched until 
the evidence from both sources establishes the fact, that the 
organ or organism under study is but the summation of modi- 
fications and elaborations of a relatively simple primordial. 
This point settled, physiology is called upon to complete the 
story. Have the functions remained the same throughout the 
series, or have they undergone a series of modifications, differ- 
entiations, and improvements more or less parallel with the 
morphological series? To answer this question, physiology 
has to appeal to the same sources of evidence as does morphol- 
ogy, namely, paleontology and embryology. 
The paleontolgical series of forms cannot of course be exper- 
imented with; but form and function are so correlated that 
the latter may often be inferred from the former, and vice versa. 
The embryological series, often including free larval stages, 
furnishes one of the grandest fields for experimental study. 
Here the physiologist has an opportunity not only to study by 
experiment but also by direct observation and inference, and 
thus to join hands with the morphologist both in methods and 
results. 
We are boaii 4 to recognize different orders of individu- 
alities,—as the cell, the tissue, the organ, the organism, the 
corm—and of course every order must have its physiology as 
well as its morphology. Morphology and physiology are 
co-extensive, each claiming the whole organic world—as it 
was, asit is and as it becomes. So long as we contradistin- 
guish form and function, we must abide by the logic of defini- 
