several days. The
glycerine dissolves the pepsin, and on filtering, a glycerine extract with
high digestive properties is obtained.

These artificial juices, when added to hydrochloric acid of the proper
strength, have high digestive powers.

Instead of _(a)_ or _(b)_ use the artificial pepsin prepared for the
market by the wholesale manufacturers of such goods.

[31] The cause of the clotting of blood is not yet fully understood.
Although the process has been thoroughly investigated we have not yet a
satisfactory explanation why the circulating blood does not clot in
healthy blood-vessels. The ablest physiologists of our day do not, as
formerly, regard the process as a so-called vital, but a purely chemical
one.

[32] Serous Membranes.--The serous membranes form shut sacs, of which
one portion is applied to the walls of the cavity which it lines; the
other is reflected over the surface of the organ or organs contained in
the cavity. The sac is completely closed, so that no communication exists
between the serous cavity and the parts in its neighborhood. The various
serous membranes are the _pleura_ which envelops the lungs; the
_pericardium_ which surrounds the heart; the _peritoneum_ which invests
the viscera of the abdomen, and the _arachnoid_ in the spinal canal and
cranial cavity. In health the serous membranes secrete only sufficient
fluid to lubricate and keep soft and smooth the opposing surfaces.

[33] A correct idea may be formed of the arrangement of the pericardium
around the heart by recalling how a boy puts on and wears his toboggan
cap. The pericardium encloses the heart exactly as this cap covers the
boy's head.

[34] "Alcohol taken in small and single doses, acts almost exclusively on
the brain and the blood-vessels of the brain, whereas taken in large and
repeated doses its chief effects are always nervous effects. The first
effects of alcohol on the function of inhibition are to paralyze the
controlling nerves, so that the blood-centers are dilated, and more blood
is let into the brain. In consequence of this flushing of the brain, its
nerve centers are asked to do more work."--Dr. T. S. Clouston, Medical
Superintendent of the Royal Asylum, Edinburgh.

"Alcoholic drinks prevent the natural changes going on in the blood, and
obstruct the nutritive and reparative functions."--Professor E. L.
Youmans, well-known scientist and author of _Class Book of Chemistry_.

[35] The word "cell" is not used