THE BLOOD. 47 



(xxv). I have observed likewise, that the blood coagulates 

 with a different appearance in proportion as the animal becomes 

 weaker; that which follows the knife begins to coagulate in 

 about two minutes ; it first forms a film or pellicle on the sur- 

 face, which extends gradually through the whole blood, yet 

 so slowly that its progress may be observed, especially if the 

 pellicle be moved from time to time. But the blood that 

 comes from the fainting animal is coagulated in an instant, 

 after it once begins. From this circumstance, that the dispo- 

 sition of the blood to coagulate is increased as the animal be- 

 comes weaker, we may draw an inference of some use with re- 

 gard to the stopping of hemorrhages, viz. not to rouse the pa- 

 tient by stimulating medicines, nor by motion, but to let that 

 languor or faintness continue, since it is so favorable for that 

 purpose; and also that the medicines likely to be of service in 

 those cases, are such as cool the body, lessen the force of the 

 circulation, and increase that languor or faintness. 1 For, in 

 proportion as these effects are produced, the. divided arteries 

 become more capable of contracting, and the blood more readily 

 coagulates ; two circumstances that seem to concur in closing 

 the bleeding orifices. 2 



It has been questioned whether bloodletting can be properly 



1 Besides giving stimulants and cordials to counteract the fainting, it is a common 

 practice in many parts of England to give women, who are flooding, considerable 

 quantities of port wine, on a supposition that it will do them service by its astringency. 

 But surely, from its increasing the force of the circulation, it must be prejudicial in 

 those cases. Perhaps man? of the remedies called styptics might be objected to for 

 the same reason. 



2 It has of late been proved by experiments, particularly by those of the ingenious 

 Mr. Kirkland, that the larger arteries, when divided, contract so as to stop the he- 

 morrhage. But the large coagula which we see in the orifices of the vessels of the 

 uterus of those who die soon after delivery, and the stopping of hemorrhages where 

 the blood-vessels were ruptured on their sides and not entirely divided, make me 

 believe that contracting the bleeding orifice is not the only method nature takes to 

 stop an hemorrhage. Her resources indeed are great, and she has often more methods 

 than one of producing the same effect. 



(xxv.) See Note xxiv. The contrary results obtained by Mr. Hey a 

 are curious. Mr. Thackrah's experiments, 5 afterwards witnessed by 

 Mr. Hey, agree with Hewson's, as Hey himself admitted. 



:1 On the Blood, 24 et seq. 8vo, Lon. 1779. Mr. Grainger's Elem. Gen. Anat. p. 41, 

 *> On the Blood, ed. 1834, p. 138. 8vo, Lond. 1829. 



