164 CIRCULATORY SYSTEM. 



one-third of the weight of the serum; in the horse, the solid will 

 bear nearly an equal ratio with the fluid portion. 



In the more perfect, or, as they have been denominated in 

 contradistinction to the others, the warm-blooded animals, the 

 blood is everywhere found, while circulating in the living body, 

 to be of a certain degree of heat ; and this it steadily preserves in 

 its circulation through the inward parts of the body, uninfluenced 

 by the surrounding temperature. In all the interior or unexposed 

 parts, the heat will exceed 100° of Fahrenheit's thermometer; it 

 has been found, however, by experiment, that this degree is not 

 equally maintained in the more superficial situations of the body : 

 what these variations are we have but little to do with, though 

 they may be ascertained by the aid of the thermometer, at any 

 time, with precision. But in the lower orders of animals, or 

 such as are called cold-blooded, the heat of the blood cor- 

 responds with that of the medium in which they live. We are 

 not, however, to suppose that the temperature of this fluid is 

 never subject to variation, even in perfect animals, for it is found 

 to be much influenced in them by disease : e. g. in the human 

 subject, in whom the heat of the body is, in health, 98°, it has 

 been known to rise to 110° during fever; and, in all superficial 

 parts, increased heat is one of the essential symptoms of inflam- 

 mation. 



The heat of the horse's blood, while flowing into a basin, is 

 100°. If the bulb of the thermometer be introduced into the 

 wound, the quicksilver will rise to about lOP. The temperature 

 of the more superficial parts of the body will, in course, vary 

 with that of the surrounding atmosphere. Mr. Hunter found 

 that the thermometer, introduced into a wound two inches deep, 

 made into the gluteal muscles of an ass, indicated 100« ; and 

 that the heat of the vagina was the same. The interior of the 

 chest of the dog he ascertained to be lOP. 



The colour of the blood is red. Not in all animals, however; 

 for in such as are called cold-blooded — in most fish, their gills ex- 

 cepted, and in insects — it is colourless and transparent. So, like- 

 wise, it is in parts even of such animals as are warm-blooded ; 

 as, for example, in the common domestic fowl, in which the 

 breast and wings are delicately white, while the legs and body 

 partake of a dusky red hue. 1 believe the blood of the horse is 

 not so high-coloured as that of a man, and that the latter yields in 

 brightness to that of a dog. All this seems to argue that colour 

 is not an indispensable property. 



The quant it 1/ of blood contained in an animal body may be 

 made matter of speculation, but cannot, for many reasons, be 

 ascertained with any degree of precision. If wc attempt to draw 



