956 The American Naturalist. [November, 
The ocean and especially the tropical ocean is, as it has always 
been, the great home of life. The forces which in cooler climates 
tend to repress and retard animal and plant life, here favor and 
force it onward. The battle for existence is here most incessant, 
its phenomena most marked. There results that boundless range 
of form and color, that exhaustless spring of individual life, 
which may well excite our wonder and our love. 
THE ETIOLOGICAL CLASSIFICATION OF DISEASES. 
gEFORE discussing this part of nosology it may be well 
to say a few words on the classification of diseases in 
general. First, we differentiate them according to that tissue 
of an organ in which the initial stage of the disease occurs, or in 
which the lesions predominate, or in other words, as to whether 
the active, or the stromatous, or supporting tissues are first 
complicated; that is, into interstitial or parenchymatous. It 
is well that this point be completely understood. 
Those who are engaged in giving instruction in our medical 
schools, as well as those members of the profession who have 
an especial fondness for pathology, generally find that not only 
the students per se, but a great many practicing physicians, either 
have, or obtain, the idea that the above classification is something, 
absolute, and that the processes are entirely limited to the tissues 
indicated in the differentiation. This is an error, but it seems to 
be a necessary failing of the text books to keep up this sharp 
differentiation, which would not be so serious had the authors but 
called attention to the fact that, while the pathological processes 
may begin in one kind of tissue, for instance the parenchymatous, 
if severe and prolonged in action they must eventually com- 
