20 TIIE DOCTRINE OF DESCENT, 
is transformed into the atomic motion of the places 
struck, a motion, invisible, it is true, but sensible’ as 
heat. But likewise the combination of the particle of 
oxygen introduced into the animal body by the respi- 
ration, with the un-oxygenated constituents of the blood, 
is a motion subject to computation, and manifesting 
itself as oxydation, combustion, or the evolution of 
animal heat. This chemical act of combustion keeps 
the animal steam-engine in motion. 
In this way, by the application of mechanical prin- 
ciples, modern physiology has traced to their causes a 
great number of organic processes, and the phantom of 
vital force, which formerly reigned paramount over the 
whole intestinal canal, incited the glandular cells and the 
muscular fibres to their offices, and glided along the 
nerves, now scarcely knows where to breed disturbance. 
Thus the investigation of nature does not shrink from 
enrolling life and the processes of life in the world of the 
comprehensible. We are foiled only at the conception of 
matter and force. But we are much further advanced 
than Schopenhauer and his adherents, who for the idea of 
Force substitute that of Will; for we have analyzed into 
their several self-conditioned momenta a multitude of 
processes, which the word “ Will,” incomprehensible in 
itself, is supposed to explain in their totality ; and much 
further also than the fashionable philosopher of the day, 
von Hartman, who regales us with the agency of the 
“unknown” in the domain of the organic world. 
“And yet,” Dubois-Reymond thus formulates another 
limit, “‘a new incomprehensible appears in the shape of 
consciousness even in its lowest form, the sensation of 
desire and aversion. It is, once for all, incomprehen- 
