The Natural Sciences in the closing years of the eighteenth century began to render the most important services to the art of medicine, and from that time onwards it has marked its progress step by step with the advances of botany, chemistry, and physics. Linnæus invented a system of the classification of plants which Adanson, Jussieu, De Candolle, and others did much to improve; the anatomy and physiology, and even the pathology of plants were closely studied, with results of the greatest value to scientific medicine. Buffon excited the interest of men of science by his declaration that there is no essential difference between animals and plants, and that all organic life follows the same plan. He explained the geographical distribution of the animal kingdom. Hunter, Blumenbach, St. Hilaire, Cuvier, and others advanced the sciences of comparative anatomy and physiology, and Lamarck divided bony animals into vertebrata and invertebrata. Cuvier, by founding the doctrine of types, explained the general plan on which animals are modelled. Pander and Baer rendered the greatest services to the study of development—the former by his researches on the development of the chick, the latter by his observations on the cleavage in the ovum. To Hunter, Kielmeyer, and Owen in a later period we owe the most important discovery—that the higher animals, even man himself, in the embryo pass through the stages of development of the lower animals.
Chemists.
Joseph Priestly discovered oxygen in 1772, and thus introduced a new chemical era. Lavoisier, however, was the first to observe the vast importance of the discovery, and Cavendish established his theories by his researches on the composition of the air, water, and acids. It is to Lavoisier’s discoveries in relation to oxygen that physiology is indebted for the knowledge of the influence of that element on respiration and the blood. Doctors looked upon it as the “air of life,” and in its excess or deficiency saw the causes of certain diseases. Fourcroy applied himself to the study of medical chemistry.
Berthollet discovered the composition of ammonia, and the bleaching properties of chlorine. He discovered chlorate of potash, and founded the doctrine of chemical affinity.
Dalton (1776-1844) by his atomic theory and his discovery of the law of multiple proportions still further advanced the science; in 1794 he first described colour-blindness.
Berzelius (1779-1848) developed the atomic theory and improved our knowledge of animal chemistry.
Gay-Lussac in 1805, with Alexander von Humboldt, discovered that water is composed of one volume of oxygen and two volumes of hydrogen.
Sir Humphry Davy (1788-1829) discovered the anæsthetic effect of nitrous oxide gas, invented the safety-lamp for miners, and greatly advanced the study of agricultural chemistry.
Dumas (1800-1884) investigated the alkaloids.
Pelletier in 1820 discovered quinine.