116 ACTION OF THE HEART; AND [BOOK I. 



the whole. These contractions constitute the pul- 

 sation, or pulse ; a criterion of health as of disease 

 which we investigate with primal anxiety, as from 

 it may be deduced the best prognostic of the state 

 of disease, especially of inflammatory ones, to which 

 this noble animal is more than any other subject, 

 from causes to be explained hereafter. 



38. Two large chambers (let us call them) and 

 two small ones, each of the latter appended to one 

 of the former, mainly contribute to the process of 

 circulation ; these, by their co-action, aid the con- 

 tractile power of the heart, compelling the contents 

 of the larger chambers to issue with much force into 

 the arteries. But, before the blood can be thus 

 again fit for circulation, nature has provided the 

 means of rendering it so, by the action and re- 

 action of these four chambers (or cavities) in the 

 heart, contributing to refine it for that purpose ; 

 one large chamber, with its small one, being placed 

 on the right side of the heart, and the like pair on 

 the left side thereof. The blood from the veins 

 flowing into the small chamber on the right side, 

 irritates its inner coats, and they each contract upon 

 its contents with nearly as much strength and quick- 

 ness as we can open and shut the hand ; — but 

 certainly not so much open, although there is a flap 

 on the entrance of each small chamber, which they 

 liken to " a dog's ear," and call by the Greek word 

 auricle, that being an ear. At each of these clos- 

 ings or contractions, the blood is forced out of the 

 small chamber into its large chamber on the same 



