l86 THE HISTORY OF BIOLOGY 



room. The brain also serves to purify the blood, which passes through it for 

 that purpose. Moreover, the cerebral cortex collects from the blood its finest 

 constituents, which give rise to the fluid that is conveyed from the brain 

 through the tubular nerve-threads out into all the different parts of the body 

 and induces movements in them. In particular Boerhaave inquired deeply 

 into the problem of muscular contraction and its relation to impulses derived 

 from the nervous system; he gives an account of an experiment to show that 

 muscular action is dependent upon the nerve and he considers that this in- 

 fluence of the nerve is due to the flowing of fluid from the brain. With regard 

 to the mechanical action of the muscles, Boerhaave highly commends Borelli's 

 mechanical investigations; the affluxion of the nervous fluid he believes takes 

 place in accordance with Mariotte's law.^ Boerhaave gives a detailed de- 

 scription of the structure and function of the genital organs, which is based 

 on the discoveries of Leeuwenhoek and de Graaf. He holds that the sperm 

 is "refined" blood; its small, living "animalcula" contain rudiments of the 

 organs of the future embryo; as eggs he regards the follicles in the ovary, 

 in this following de Graaf; conception takes place as a result of the "living 

 elements" of the sperm penetrating the pores of the egg. 



As a whole Boerhaave 's biological theory must be considered to come 

 far nearer our modern ideas than either Hoffmann's or Stahl's — this both 

 on account of what he knows and above all on account of what he considers 

 it impossible to know. His insight into the limitations of natural science 

 really testifies more than anything else to his greatness; as regards facts, we 

 cannot expect of him more than it was possible for his age to attain. But it 

 is just his deliberateness that it has been difficult both for his contemporaries 

 and for posterity to understand; the desire to solve the ultimate riddle of 

 life has again driven the philosopher beyond the limits of what science can 

 attain with the means available. We shall leave Boerhaave, clear-sighted 

 and conscious of his own limitations, and shall proceed to consider a scientist 

 who sought to solve the riddle of life along speculative lines and who ex- 

 pended on this endeavour one of the richest and most fertile geniuses known 

 to history — namely, Swedenborg. 



The son of Bishop Jesper Swedberg, a famous hymn-writer and preacher 

 of the Swedish Church, Emanuel Swedenborg was born in 1688 and received 

 a thorough school and university education at Upsala, where he grew up; 

 having completed which, he spent several years in England and on the 

 Continent, studying principally natural sciences, both theoretical and ap- 

 plied. Having returned home, he served as a military engineer during the 

 last fighting years of Charles XII, then became assessor of the board of mines, 



^ Boerhaave undoubtedly refers to the hydrostatic experiment which goes by the name of 

 Mariotte's bottle; how its phenomena are to be applied to the nervous and muscular functions 

 is, however, not clearly stated. 



