are most advantageous.

If we can preserve the organs, we may expect to also keep alive the
tissues and cells of which they are composed. Biologists have studied
these problems, too, and have also obtained in this department some
very interesting results.

The cells which live naturally isolated in the organism, such as the
corpuscles of the blood and spermatozoa, were the first studied. Since
1910 experiments on the survival of tissues have multiplied and at the
same time more knowledge has been obtained concerning the conditions
most favorable to survival and the microscopical appearances of the
tissues so preserved. In 1910 Harrison, having placed fragments of an
embryo frog in a drop of coagulated lymph taken from an adult, saw them
continue their development for several weeks, the muscles and the
epithelium differentiating, the nervous rudiments sending out into the
lymph filaments similar to nerve fibers. Since 1910 with the aid of Dr.
Minot, I have succeeded in preserving alive the nerve cells of the
spinal ganglia of adult dogs and rabbits by placing them in
defibrinated blood of the same animal, through which there bubbled a
current of oxygen. At zero and perhaps better at 15 deg.-20 deg., the structure
of the cells and their colorable substance is preserved without notable
change for at least four days; moreover, when the temperature is raised
again to 39 deg., certain of the cells give a proof of their survival by
forming new prolongations, often of a monstrous character. At 39 deg. some
of the ganglion cells which have been preserved rapidly lose their
colorability and then their structure breaks up, but a certain number
of the others form numerous outgrowths extremely varied in appearance.
We have, besides, studied the influence of isotony, of agitation, and
of oxygenation, and these experiments have enabled me to ascertain the
best physical conditions required for the survival of nervous tissue.
In 1910, Burrows, employing the technique of Harrison, obtained results
similar to his with fragments of embryonic chickens. Since 1910 Carrel
and Burrows applied the same method to what they call the "culture" of
the tissues of the adult dog and rabbit; they have thus preserved and
even multiplied cells of cartilage, of the thyroid, the kidney, the
bone marrow, the spleen, of cancer, etc. Perhaps Carrel and his
collaborators may be criticized for calling "culture" that which is
merely a survival, but there still