108 VETERINARY STATE BOARD 



What are the principal differences between arterial blood and venous 

 blood? 

 Arterial blood contains more oxygen and less carbon dioxide, 

 more water, fibrinogen, extractives, salts and sugar, fewer blood- 

 corpuscles and less urea; its temperature is, on the average, 1° C. 

 lower. Venous blood is darker in color, due to the diminution in the 

 oxygen-content. 



What is the color of the blood in the renal veins? Why? 



Dark-blue, same as all venous blood. In its passage through the 

 kidney, the blood loses oxygen and takes up carbon dioxide, there- 

 fore, it is venous in character as it leaves this organ. 



What salts render the blood alkaline? 



The phosphate and bicarbonate of soda. 



Describe the process of coagulation of the blood. 



The blood first becomes a jelly and then a firm clot. The clot con- 

 tracts and squeezes out a fluid, serum. As this serum accumulates, 

 the clot sinks. The substance which brings about coagulation is 

 fibrinogen, which, being acted upon by the ferment, thrombin, 

 produces fibrin. 



Of what does a blood clot consist? How would you demonstrate the 



presence of fibrin in freshly drawn blood? 



A blood clot consists of fibrin and blood-corpuscles. Fibrin 



may be demonstrated by defibrinating freshly drawn blood. This 



is accomplished by whipping the blood with a rod or bunch of 



twigs ; the fibrin separates rapidly and collects on the rod. 



What influences the combination of haemoglobin vi^th oxygen? 



The atmospheric pressure of oxygen being higher than the 

 pressure of the oxygen in the venous blood as it arrives at the heart 

 may play a very small part in influencing the taking up of oxygen by 

 the blood; but the strong affinity of haemoglobin and oxygen for 

 each other is of greater influence. This subject has not been satis- 

 factorily explained. 



How is oxygen carried in the blood and where is it exchanged for 

 carbon dioxide? 

 It is carried in the blood united with the haemoglobin, as oxy- 

 haemoglobin. It is exchanged for carbon dioxide in the tissues. 



When serum is used subcutem for therapeutic purposes, what danger 

 attends its transfer from one genus to another? 

 Haemolysis, breaking down of red blood-corpuscles and liberation 

 of hsemoglobin, occurs. 



