208 PHYSIOLOGY. 



vessels is constantly being acted upon by two opposing influences: 

 one with, a tendency to promote coagulation, the other to oppose it 

 antithrombin. In health the former never gains the ascendency. 



Haemorrhage and its Effects. It is common knowledge that a 

 very abundant loss of blood causes death. The blood has for its 

 functions to insure the physical conditions of the life of the cells 

 as well as to maintain an excitability of the nerve-cells which 

 govern respiration and circulation. Every considerable loss of blood 

 disorders cell-life in the organism,, tending to cause death. Necrosis 

 very soon manifests itself when a member has by some procedure 

 been deprived of its normal supply of blood. When the loss of 

 blood has been from the whole system, and not confined to any 

 member, a general death precedes the local death of the cells, 

 because, the oxygen not going to the cardiac and respiratory cen- 

 ters, the functions of the heart and lungs are arrested. The prin- 

 cipal symptoms of great loss of this vital fluid are general paleness 

 and lower temperature of the cutaneous surface, oppression, breath- 

 lessness, stoppage of the secretions, with final general convulsions 

 of anaemia. 



The quantity of blood which can be lost without causing death 

 varies according to age, sex, temperature, etc. The loss of some 

 cubic centimeters in the newborn, of a half-pound in an infant of 

 one year, or of half the quantity of blood in an adult, is capable of 

 causing death. Women bear the loss of blood much better than men 

 because of the periodical haemorrhages to which they are subject. 



The renewal of the blood appears to be accomplished rapidly, 

 although the time of withdrawal plays an important role in deter- 

 mining whether there will be attending fatality. If the loss has not 

 been too rapid, the fluid part of the blood and its dissolved salts 

 is replenished by withdrawal from the lymph of the tissues. Later 

 the albumin is restored, but a much longer period is required for 

 replenishment of the corpuscles. The amount of haemoglobin is 

 diminished in proportion to the amount of bleeding. 



SHOCK very materially affects the results of haemorrhage. When 

 the sensibilities are deadened temporarily by anaesthetics, less seri- 

 ous results follow the loss of a given quantity of blood than when 

 the same quantity escapes through accident. 



TRANSFUSION. This is a process by which blood is conveyed 

 from one animal to the vascular system of another. It was shortly 

 after Harvey's discovery of the circulation of the blood that this 

 operation was first practiced by Denis, of Paris. He transfused with 



