170 NATURE AND LIFE. 
due to the rupture of the cells containing the coloring- 
matter of the petals. This matter, freed from its cellular 
covering, disappears on simply washing with water, and 
the flower becomes almost white. In leaves showing two 
surfaces of different shades, as the Begonia discolor, a kind 
of mutual exchange of colors between the two surfaces 
has been noticed. 
Il. 
The physiological phenomena just spoken of are usually 
confounded in books with the facts of electric medical 
treatment, and it seems better to distinguish the two class- 
es. The true method consists in first explaining the phe- 
nomena displayed in the healthy crganism, as the only way 
of understanding afterward those that are peculiar to dis- 
orders. Electric treatment forms a group of methods to 
be classed among the most efficacious in medicine, pro- 
vided they are applied by a practitioner well trained in the 
theory of his art. Indeed, the most thorough physiologi- 
cal knowledge is essential for the physician who would 
make the electric currents erviceable. Mere experimenting, 
even the most sagacious, must here be barren of good re- 
sults—a fact of which it is well to remind those who im- 
pute to the method itself the failures it meets with in un- 
skillful hands. It is true that, since the days of Galvani 
and Volta, physicians have used galvanism in the treat- 
ment of many diseases. Early in the century, galvanic 
medicine was much talked of, and supposed to be the uni- 
versal panacea. Galvanic societies, journals, and treatises, 
undertook to spread its usefulness. The fashion lasted a 
certain time, and would perhaps have grown indifferent, 
when the discovery of induced electricity, due to Faraday, 
in 1832, called professional attention once more to the vir- 
tues of the electric fluid, and led to a new and interesting 
range of experiments. Yet it is likely that the true sys- 

