The Blood and Lymph. 89 



fereuce in the contents of the red blood cells before and 

 after birth are made use of in the human race for the 

 detection of crime. These cells contain a nucleus before 

 birth, after they do not, so that in case of the finding of 

 a dead child, if no nuclei are found in its red blood cells 

 it is assumed that it has lived a day or two, if nuclei are 

 found the child was still born. 



White blood cells have an average diameter of -jsYo °f 

 an inch. 



The amount of blood in the body varies with the ani- 

 mal, it has been estimated in the horse to be about equal 

 to T *g of the body weight, in man about fc 



The blood pump (heart) is a hollow muscle, cone 

 shaped, and in the horse about 5^ lbs. in weight. It is 

 situated in the chest cavity between the right and left 

 lungs, its apex being downwards. It is divided into two 

 well marked halves, each of which is again divided into 

 an upper chamber or auricle and a lower chamber or 

 ventricle, consequently we speak of the right side of the 

 heart and the right auricle, or ventricle, as the case may 

 be. The division between the auricles and ventricles is 

 not as perfect, being only by valves, as is the division 

 between the right and left heart. These valves serve 

 another purpose, that of preventing a backward move- 

 ment of the blood, in order to do so efficiently, little 

 cords of great strength are attached to the valves and 

 thus prevent them being pressed back out of place, such 

 provision is needed when one thinks of the enormous 

 pumping power of this organ. Each chamber of the 

 heart has certain openings to it and from it, all guarded 

 by valves, for example, in the right ventricle are two 



