EMANCIPATION OF SCIENTIFIC RESEARCH. 43 



to separate completely the domain of facts from the 

 domain of hypotheses. 



Excessive Use of Hypothetical Agents in Physio- 

 logical Explanations. — It may be said that in the 

 early part of the nineteenth century, in spite of the 

 efforts of a few real experimenters from Harvey to 

 Spallanzani, Hales, Laplace, Lavoisier, and Magendie, 

 the science of the phenomena of life had not followed 

 the progress of the other natural sciences. It remained 

 in the fog of scholasticism. Hypotheses were mingled 

 with facts, and imaginary agents carried out real acts, 

 in inexpressible confusion. The soul (animism), the 

 vital force (vitalism), and the final cause (finalism, 

 teleology) served to explain everything. 



In truth, it was also at this time that physical 

 agents, electric and magnetic fluids, or, again, chemical 

 affinity, played an analogous part in the science of 

 inanimate nature. But there was at least this 

 difference in favour of physicists and chemists, that 

 when they had attributed some new property or 

 aptitude to their hypothetical agents they respected 

 what they attributed. The physiological physicians 

 respected no law, they were subject to no restraint. 

 Their vital force was capricious; its spontaneity made 

 anticipation impossible; it acted arbitrarily in the 

 healthy body; it acted more arbitrarily still in the 

 diseased body. All the subtlety of medical genius 

 was called into play to divine the fantastic behaviour 

 of the spirit of disease. If we speak here of physio-' 

 logists and doctors alone and do not quote biologists, 

 it is because the latter had not yet made their 

 appearance as authorities ; their science had remained 

 purely descriptive, and they had not yet begun to 

 explain phenomena. 



