HEART AND BLOOD. 71 



and then because it is forced from the capillary veins into the 

 smaller ramifications, and from these into the larger trunks 

 by the motion of the extremities and the compression of the 

 muscles generally. The blood is thus more disposed to move 

 from the circumference to the centre than in the opposite di- 

 rection, were there even no valves to oppose its motion ; whence 

 that it may leave its source and enter more confined and 

 colder channels, and flow against the direction to which it 

 spontaneously inclines, the blood requires both force and an 

 impelling power. Now such is the heart and the heart alone, 

 and that in the way and manner already explained. 



CHAPTER XVI. 



THE CIRCULATION OF THE BLOOD IS FURTHER PROVED FROM 

 CERTAIN CONSEQUENCES. 



THERE are still certain phenomena, which, taken as conse- 

 quences of this truth assumed as proven, are not without their 

 use in exciting belief, as it were, a posteriore ; and which, 

 although they may seem to be involved in much doubt and ob- 

 scurity, nevertheless readily admit of having reasons and causes 

 assigned for them. The phenomena alluded to are those that 

 present themselves in connexion with contagions, poisoned 

 wounds, the bites of serpents and rabid animals, lues venerea 

 and the like. We sometimes see the whole system con- 

 taminated, though the part first infected remains sound; the 

 lues venerea has occasionally made its attack with pains in the 

 shoulders and head, and other symptoms, the genital organs 

 being all the while unaffected ; and then we know that the 

 wound made by a rabid dog having healed, fever and a train 

 of disastrous symptoms nevertheless supervene. Whence it 

 appears that the contagion impressed upon or deposited in a 

 particular part, is by and by carried by the returning current 

 of blood to the heart, and by that organ is sent to contaminate 

 the whole body. 



In tertian fever, the morbific cause seeking the heart in the 

 first instance, and hanging about the heart and lungs, renders 

 the patient short-winded, disposed to sighing, indisposed to ex- 

 ertion; because the vital principle is oppressed and the blood 



