LECTURES ON CHEMISTRY. 
763 
once-thought worthless sea-weed a substance is obtained, which, 
by union with flint, forms that useful article glass, or, when 
combined with fatty matters, soap. The hoofs and offals of ani- 
mals yield another of these alkaline bodies, highly useful in medi- 
cine, as we shall have occasion to shew you hereafter; while the 
fairest of Eve’s daughters use it as an exhilarating perfume, know- 
ing not whence it is derived. 
From our common table salt, an element is procured by chemic 
art possessing properties unequalled, perhaps, in value. By 
it our linens are bleached, and thus it conduces to our com- 
fort and our happiness, and, as a medicament, it has the singu- 
lar power of destroying putrid effluvia, which it does effectually, 
by at once decomposing them, thus preventing the access of dis- 
ease and counteracting the cause of it. Before the advances 
which chemistry has lately made, perfumes were too frequently 
employed whenever a contagious malady prevailed, and thus the 
poison was rendered even more effectual in accomplishing its dire- 
ful ravages ; but, by the use of the elementary substance chlorine, 
it is rendered perfectly innocuous. Nor is this all ; — its com- 
pounds, in the hands of the scientific man, relieve many of the 
diseases which are the common lot of mortals. 
The advantages derived from chemistry in the application of its 
principles to medicine is a most important subject. Of the ori- 
gin of the science of medicine we have not time at present to 
speak, but we shall hereafter have many opportunities of illus- 
trating it. 
Chemistry enables us to separate the active principles of vege- 
table substances from an immense mass of inert matter with 
which they are often united ; and although the vegetable alka- 
loids have not as yet been much employed in veterinary practice, 
nor even generally by the practitioner of human medicine, on ac- 
count of their expensiveness, yet, I doubt not, that in time other 
means of separation will be discovered than those which now 
exist, and then they will be extensively used ; for we shall be en- 
abled to speak almost with certainty of the action of the vegeta- 
ble agent we are desirous of administering. At present, the ac- 
tivity of vegetables much depends upon the nature of the soil, the 
influence of climate, and its variations ; and, more than all these, 
upon the mode of cultivation and preparation. 
Many vegetables owe their activity to vegetable extractive, and 
this it is desirable to obtain isolated ; for, oftentimes, the stomach, 
from the effects of disease, is unable to separate the active from 
the inert matter. Pharmaceutical chemistry assists usm eftecting 
this. The operation of others depends upon the presence of an 
essential oil ; and this one of the commonest operations of the 
