HIS WORKS. Iv 



from escaping into the latter; whilst the office of the semi- 

 lunar valves, at the origins of the pulmonic artery and aorta, 

 he declared, from their position, must be to prevent the en- 

 trance of the blood of the great arterial trunks into the heart. 

 Fabricius, the master of Harvey, may be said to have perfected 

 anatomical knowledge in regard to the valves of the veins for 

 he by no means first directed attention to their existence, or 

 discovered them, as is generally asserted. Fabricius believed 

 that their function was to act as obstacles to congestions of 

 blood, as strengtheners of the veins and preventives to their 

 becoming over-distended. 



Another long and much agitated point in the anatomy of 

 the sanguiferous system, was the state of the septum ventri- 

 culorum of the heart, in respect of permeability or impermea- 

 bility. The reason of the vast importance attached to this 

 point was connected with the ancient, and, in Harvey's time, 

 generally accredited hypothesis of the Three Spirits the 

 natural, the vital, and the animal. The hypothesis to be 

 brought into play, was presumed to require the intermixture 

 in the heart of the two kinds of blood that were held appro- 

 priate to the two ventricles and to the arteries and veins re- 

 spectively, and that were farther believed to meet in the 

 cavities of the cranium, thorax, and abdomen, from which they 

 returned to the heart by the way they came, for a fresh supply 

 of the spirits (now exhausted or enfeebled), under the agency 

 of which all the important operations of the body were be- 

 lieved to be accomplished. 



Now, Galen, the author of this hypothesis, in order to 

 obtain an admixture of the two kinds of blood, feigned and 

 described the partition between the two ventricles, either as 

 perforated like a sieve, or as filled with depressions of depth 

 sufficient to entitle them to be viewed as constituting a kind of 

 third ventricle the last assumption doubtless to accommodate 

 each order of spirits with its own particular officine or workshop. 



