72 PROPERTIES OF 



by the digestive organs, before they are mixed with blood. 

 And as they are most of them cooling and sedative, they pro- 

 duce nausea and languor of the stomach, and lessen the force 

 of the vascular system. And as the properties of the blood 

 seem to depend upon the action of the vessels (see Note xxiv), 

 these salts may thus, by affecting the vessels, produce changes 

 on the blood very different from what might have been sus- 

 pected, from observing what takes place when a large quantity 

 of them is mixed with the blood out of the body. 



The blood is not coagulated (I do not mean thickened, for 

 it is indeed thickened) by cold, but on the contrary, has its 

 disposition to coagulate lessened, and even entirely taken off, 

 if the exposition to cold (xxxix) be long continued. When 

 therefore the blood in the basin jellies, it is not the cold that 

 produces this effect, nor is it the want of motion ; for although 

 the blood by being at rest will jelly at last, yet it will not 

 do it in the time the coagulation takes place in the basin; 

 which in the blood of healthy persons is in seven or eight 

 minutes after being received from the vein. The coagulation 

 of the blood in the basin is therefore probably owing to the 

 air (XL). 



When the blood is at rest in the bo$y, it will at last coagu- 

 late merely for want of motion ; but this coagulation takes 

 place with different appearances from that of the blood in a 

 basin, for it begins in ten or fifteen minutes, and is not com- 

 pleted in three or four hours ; whilst the blood of the same 

 animal, taken out of the veins, and exposed to air, will begin 

 to jelly in three or four minutes, and will be completely jellied 

 ia seven or eight (XLI). 



The effect that air has upon the blood is not immediate 

 on its application, but takes place sooner or later, in different 

 circumstances of health ; in some cases the blood is coagulated 

 in a few seconds after it has been exposed to the air, in others 

 not in less than an hour and a half, or perhaps more, as appears 

 from Experiment 14th. 



(xxxix.) Concerning the effects of a low temperature and of freezing 

 on coagulation, see Note xi. 



(XL.) The effect of air on coagulation is mentioned in Note xn. 



(XLI.) On the effect of living tissues on coagulation, see Note xui ; 

 on the slow coagulation of the blood in the body after death, see Note x. 



