3(1^ RE-CONVERSION OF VENOUS BLOOD. 



an ear. At each of those closings or contractions, the blood is forced out of 

 the small chamber into its large chamber on the same (right) side, through a 

 small door-way, or valve, which opens only inwards, the door being too large 

 for the door-way. By the way, these valves are very numerous in the animal 

 system, principally as regards the circulation of blood in the veins ; and the 

 reader will do well to recollect, when I speak of valves in future, the illustra- 

 tion just given by comparing the same to a door-way, which bears a near re- 

 semblance to the valve. In the performance of this office, the heart may be 

 said to have three several motions belonging to it: 1st, a quick one, by the 

 contractions of the smaller chambers upon their contents: 2d, the contractions 

 of each large chamber upon its contents, being just half the number of throbs 

 made by the first mentioned : and, 3d, the vibration or tremor of the whole 

 heart in consequence of all those motions. 



Well, on the right side still, the large chamber being filled with venous 

 blood through the valve, or door-way, from the small one, becomes in like man- 

 ner irritated so as to contract upon its contents, and to drive it out somewhere 

 or other. Back to the small chamber it can not possibly go ; the valve does not 

 open the way, as I have just now said ; and therefore it issues with much more 

 force through another valve into a short artery, which soon opens into two, 

 like the letter Y, the heart being supposed at the bottom of the letter. Up 

 rushes the blood to the top of the two branches — where it meets with — What! 

 What do you think it meets with, gentle reader! 



Hefe, however, let him stop a little, and consider awhile ; for, upon his right- 

 ly understanding what now becomes of the blood (thick, dark, and unservice- 

 able as it is), and how, in a trice, it becomes healthy, of a bright scarlet colour, 

 and invigorating, mainly depends his being able to comprehend, by-and-by, 

 what I shall have to offer concerning the diseases to which a vitiated or cor- 

 rupt state of the blood gives rise. He will not, otherwise, make out sufficient- 

 ly clear in what manner the blood of an animal can contract and retain that 

 morbid state which shall predispose it towards acquiring a constitutional dis- 

 ease that, however differently named according to the parts whereon it may 

 fix, has but this one common origin for the entire series. To this page, then, 

 I shall frequently refer him when speaking to these points more in detail, here- 

 after; and he had best, also, keep the book open at this place, whenever he 

 may be endeavouring to comprehend what the learned veterinarians of the 

 present day are striving to say respecting "the circulation," as they quaintly 

 term it. Another of them, speaking upon the topic I have just brought to a 

 conclusion, says, " The heart is divided into two cavities, termed ventricles, 

 each having an auricle, resembling a dog's ear. The blood-vessels proceed 

 from these [those] cavities, the arteries from the ventricles, the veins from the 

 auricles, &c." All which is very true, but not very intelligible to the gene- 

 rality of readers; and yet is the author, who thus speaks, (Mr. White, in vol. 

 i. p. 63) said to be the plainest spoken among the moderns ; indeed, were he 

 any thing else than a good one, I should not have deemed him worthy of this 

 rebuke. 



39. The Blood, as I have said, rushes out of the large chamber on the right 

 side of the heart into an artery that soon divides into two branches; whereof 

 one enters each lobe of the lungs, and there disperses, through certain cella^ 

 the blood with which it is constantly supplied. Here lies the the secret! At 

 this point it is, that health or disease (at least a predisposition to one or the 

 other) is imbibed and engendered in the blood. The lungs having rcceivea 

 the thick discoloured blood from the right side of the heart, and being the re- 

 ceptacles of the air we all breathe, do, by means of that air, bestow upon tho 

 blood afresh the principles of Ufe, and health, and vigour. The cells, or tubes, 

 thr'^'ijjh which the bloo«.l passes in the lungs, termed pulmonary, are eight in 



