On Muscular Motion and Animal Spirits 275 



who hold that the thicker and more fixed part of the 

 blood is detained in the substance of the spleen, and 

 that it, by being long kept, acquires a fermentative 

 character ; for if particles of blood anywhere cease 

 from movement and stagnate, these particles will 

 prevent those immediately following from continuing 

 their motion, and thus, the circulation of the blood 

 being in that part interrupted, swelling and inflamma- 

 tion will necessarily result. Moreover, the numerous 

 branches of nerves disseminated in the spleen seem 

 to serve no other purpose but that of conveying 

 fermentative particles. 



Besides, as, when the fermentation in the spleen is 

 too remissly performed the blood becomes too crude, 

 so on the other hand if it is increased beyond a right 

 extent the mass of the blood acquires a somewhat 

 dried and atrabilious character. Indeed, as in fire 

 the nitro-aerial particles effervescing most intensely 

 with the sulphureous particles burn them up in an 

 instant and turn them into smoke, as we elsewhere 

 show, so also if in the parenchyma of the spleen 

 the nitro-aerial and the saline-sulphureous particles 

 work together too much, it comes to pass that these 

 particles become to some small extent dried up and 

 sooty, and from them, fixed in the substance of the 

 spleen, its dark purple colour seems to come. But 

 that atrabilious diathesis of the blood may arise from 

 a twofold cause. 



I. If the saline-sulphureous particles of the blood 

 are detained in the spleen by reason of its paren- 

 chyma being obstructed ; for thus they, by effervescing 

 too long with the nitro-aerial particles, become 

 torrefied and dried. Indeed the mass of the spleen 

 seems to be composed of two kinds of vessels ; of which 

 one, consisting of nervous fibres, is destined for the 



