384 The American Naturalist. [May, 
need of a rational method of observation and experiment, 
was none other than the discovery of the circulation of the 
blood. | 
With the announcement of this to the world in 1628, what 
we have called the fourth period of physiological history 
begins. Harvey’s book, “ De Motu Cordis,” is a model record 
of an ideal scientific investigation. The accumulation of an 
abundance of the essential facts, obtained by a most careful 
and systematic study of nature, the clear understanding of 
their logical positions and their mutual relations, and then, 
unhampered by scholastic systems and a priori considerations, 
but guided only by a regard for truth, the orderly arrange- 
ment of the accumulated material into the one possible 
rational system—such was Harvey’s method. The result was 
incontrovertible. The full title of Harvey’s work is “ Brerei- 
tatio Anatomica de Motu Cordis et Sanguinis in Animalibus,’ bat 
Harvey himself, being a physician, and his contemporaries 
and followers naturally enough considered more especially the 
human bearings of the established facts. For two hundred 
years after, discovery followed discovery, and the permanent 
foundations of the various subdivisions of physiology were 
laid—circulation, respiration, animal heat, the functions of 
the central nervous system and of the peripheral nerves, 
movement, animal electricity, reproduction, optics and acous- 
tics. Haller’s well-known contribution was that of the inde- 
pendent irritabilitv of muscle. Of perhaps as much value 
were his complete knowledge of physiological literature and 
his activity in writing. In 1747 he published a text-book, the 
“ Primae Lineae Physiologiae,” and in 1757 the large and n 
plete “ Elementa Physiologiae Corporis Humani.” These books 
were widely circulated and the entity of the science a for- 
ever established. The title of Haller’s larger work, por 
ments of the Physiology of the Human Body,” indicates K 
its “ anthropocentric ” character was stamped firmly aain 
By its independent growth, its subordination to medicin? ae 
however, already weakened: ` 
To enumerate its advances during the past fifty 
the fifth period, would be a task of great proportions. 
-SİX years 
