22 



infants have their pulse 120, and from thence, down 

 to old age, it grows slower, to 60 in a minute. A 

 feverish pulse begins at &6 per minute; it is excessive 

 at ISO or 140, which is the number of the pulse with 

 which a person dies. The pulse beats slower in 

 winter, and quicker in summer, by about ten strokes 

 per minute ; and under the torrid zone, it grows 

 quicker to 120. , 



8. A vein is a hollow canal, which receives the bfood 

 from the artery, and conveys it back to the 'heart. 

 The chief veins are three, the vena cava, which pours 

 the blood through a wide passage into the right ven- 

 tricle of the heart ; the pulmonary vein, which in 

 like manner pours it into the left ventricle ; and the 

 Yena portae, which docs not, like the two former, end 

 in a large trunk, but spreads itself at each extremity 

 into numerous branches. 



In the cavity of the \eins there are certain thin tu- 

 nicles, which are termed valves. These, during the 

 regular motion of the blood, lie close to the side of the 

 inner coat; but in case of any obstruction, recede 

 from it and clo,ie the passage, to prevent the blood's 

 failing back. 



9. The lymphatic vessels are small canals full of 

 Talves, consisting of a thin transparent tunic, which 

 convey an extremely clear liquid into the mass of blood. 

 Probably these (as well as the veins) ami all the other 

 vessels, are only continuatior.s of the arteries. 



It has bee-n lately discovered that the lymphatic vcs. 

 sels have two coats, betwixt which there are innumer- 

 able fine filaments containing a nutricious juice, which 

 is conveyed into all parts of the body by a motion from 

 the centre to the circumference, and returns through 

 the inner pipes of the same watry vessels; but this 

 juice, when returning, is no more water or dew, ,but 

 ferment, and the vessels may be termed ferment-vessels. 

 This ferment is conveyed into the blood by a motion 

 from tl e circumference to the centre. 



