THE BLOOD. 65 



From this formula it will be seen that the two bicuspid 

 teeth in the adult are the successors of the two molars in 

 the child. They differ from them, however, in some 

 respects, the temporary molars having a stronger likeness 

 to the permanent than to their immediate descendants, the 

 so-called bicuspids. The temporary incisors and canines 

 differ but little, except in their smaller size, from their 

 successors. 



CHAPTEE VI. 



THE BLOOD. 



ALTHOUGH it may seem, in some respects, unadvisable to 

 describe the blood before entering upon the physiology of 

 those subservient processes which have for their end or 

 purpose its formation and development, yet there are 

 many reasons for taking such a course, and we may 

 therefore at once proceed to consider the structural and 

 chemical composition of this fluid. 



Wherever blood can be seen as it flows in the vessels of 

 a living part, it appears a colourless fluid containing 

 minute particles, the greater part of which are red, and 

 give the blood its colour. The fluid is named liquor 

 sanguinis ; the particles are the Hood and lymph-corpuscles, 

 or cells. The structural composition of the blood may be 

 thus expressed : 



Liquid Blood. 



Corpuscles . . . _. . . \ Clot (containing also 

 Liquor Sanguinis 



Fibrin j more or less serum.' 



When blood flows from the living body, it is a thickish 

 heavy fluid, of a bright scarlet colour when it comes from an 

 artery ; deep purple, or nearly black, when it flows from 



