The next and last group is that of Food Substances containing alkaloids,
which act upon the nervous system as stimulants or sedatives. The
principal examples are Tea, Coffee, Cocoa, Tobacco, Hemp, and Opium.
Tea and Coffee have hardly any other properties in common than the
possession of an alkaloid called _Theine_ or _Caffeine_, which is
identical in the two. Chocolate contains a peculiar alkaloid called
_Theobromine_. Paraguay tea or “maté” is the only other substance
extensively used as a dietetic infusion that contains _theine_; in South
America it occupies the same position in domestic economy as Chinese tea
does in this country. Case 46 exhibits the chemical analysis of a pound
of ordinary good Chinese Tea; and in Cases 47, 48, and 99, contiguously
placed, are numerous samples of tea from China, Japan, Java, Brazil, and
East India.
The analysis of a pound of Coffee is shown in Case 50; and many samples
of raw coffee from various parts of the world are exhibited. The
visitor’s notice is directed to the printed descriptive label concerning
Coffee, which is suspended near the case containing the analysis.
_Cocoa_ is represented by the analysis of a pound of Cocoa paste in Case
53, and by a series of the fruit pods containing the seed or nuts,
presented by Messrs. Fry and Son, of Bristol, as well as by various
preparations and confections. The distinguishing feature of its
composition consists in the large quantities of fat and albumen which it
contains; so that Cocoa not only acts as an alternative through its
_theobromine_, but as a force-producing and flesh and force-producing
food. Samples of the commercial varieties of the nuts or seeds from
various countries are exhibited.