THE VERTEBRATE ANIMAL — SUBPHYLUM VERTEBRATA 



393 



was mentioned in connection with respiration. Due to this sub- 

 stance, the cells have oxygen-carrying power. The white corpuscles 

 or leucocytes are of several varieties and they are amoeboid in char- 

 acter. These cells may make their way among cells of other tissues 



Veins from upper. 

 part of Bcxjy 



Lymphatics 



Thoracic duct - 



^uporiop vena cava 

 'PulmonaP3^ artary 



Ui^ht aupicla — 



Infcpiop vena cava- 



fli'^ht vcntpiclG 



Lacteal^ — 



Hepat 



ic vain. ■ 



Veins from lowcp 

 papt of Body 



Lympfiaticj — 



Arteries to upper* 

 part of Body 



Pulmonapy vein 



— Left auricle 



- Left ventpjclc 



ArtGplo3 to lowcp 

 par>t of Body 



Fig. 219. — Diagram of circulation of the blood in a mammal. The oxygenated 

 blood is shown in black ; the venous blood in white. The lymphatics are the black 

 irregular lines. (From Pettibone, Physiological Chemistry, published by The C. V. 

 Mosby Company.) 



where they engulf bacteria and foreign matter. Upon exposure to 

 air the dissolved fibrinogen in the blood becomes fibrin and forms a 

 clot which is semisolid and blocks flow of blood from most wounds. 

 The remaining' fluid after the blood clots is called serum. Lymph 



