470 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



bicarbonate and sodic phosphate, most marked when the blood is freshly 

 drawn, and decreasing rapidly in intensity until coagulation occurs. 



Blood has a peculiar odor which varies in different animal species, 

 and in certain animals, as in the cat, dog, sheep, and goat, is charac- 

 teristic of the species. This odor is due to the presence of certain vola- 

 tile, fatty bodies contained in the blood-plasma, and may be readily 

 developed by treating the blood with sulphuric acid. 



The temperature of the blood varies in different animals, and depends 

 upon the oxidation processes continual^ occurring in the tissues. In 

 man and the domestic mammals the temperature varies from 31.5° to 

 38° C. In birds it is always higher than in mammals, and may rise as ' 

 high as 44.03° C. even in a state of health. The arterial blood is, as a 

 rule, warmer than venous blood, as the conditions for radiation of heat 

 are more favorable in the latter than in the former. The temperature of 

 the blood of the hepatic and portal veins is warmer than other venous 

 blood, and the blood of the right side of the heart is warmer than that 

 of the left heart. 



The quantity of blood varies in different animals and in the same 

 species of animal at different periods of life. Various methods have been 

 proposed for determining the amount of blood contained in the body. 

 The method which is now generally adopted as giving the most reliable 

 results is to bleed an animal to death and measure the amount of blood 

 collected. The blood-vessels are then washed out with dilute saline solu- 

 tion until the fluid which issues from the veins comes out entirely color- 

 less, and the various washings are collected and mixed. A known 

 quantity of blood is then diluted with saline solution until it acquires 

 the same tint as a measured quantity of the washings collected from the 

 veins. From the data so obtained the amount of coloring matter in the 

 washings may be estimated. The entire body is then minced, washed 

 free from blood with saline solution, filtered, and the amount of coloring 

 matter in the washings estimated as before. The quantity of blood in 

 the two washings, together with the blood first drawn, give the total 

 amount in the body. 



Estimated in this way, the total amount of blood in the human body 

 has been fixed at y'j of the body weight ; in the rabbit at -jL of the body 

 weight ; dog, T ^ of the body weight ; cat, ^\ ; frog, T ' 5 ; mouse, ^ ; the 

 guinea-pig, t 't, ; bird, T V— rV ; fishes, T \— r ' ¥ . No reliable estimates 

 exist as to the amount of blood in the larger domestic animals. Colin 

 states that the amount of blood in the ox amounts only to J s of the 

 body weight, but this is probably a low estimate. In animals bled to death 

 the amount of blood retained in the body depends upon the amount of 

 adipose tissue : the fatter the animal, the more blood remains in the body 

 after slaughtering. In thin cattle the amount of blood which escapes 



