230 THE BLOOD 



vessels supplying the aforesaid organs after having previously ligated 

 them at the same time. The tissues were then subjected to the chromo- 

 metric test described previously. 



Loss of Blood. — The blood escaping from a wound exhibits certain 

 differences in color which are dependent upon differences in the loca- 

 tion and extent or depth of the lesion. A bright red color signifies 

 arterial bleeding and a dark red color a venous extravasation. In 

 either case, the blood escapes in large volume, and, in arterial hemor- 

 rhage, under a considerable pressure. In capillary bleeding, on the 

 other hand, the blood oozes out slowly as fine droplets which finally 

 coalesce to form a flat coagulum. Its color is intermediate, provided, 

 of course, that its oxygenation has not been interfered with by such 

 conditions as venous stasis or arterial hyperemia. Hemorrhages are 

 described as primary and secondary, the latter term being appHed 

 to those losses of blood which may occur after operations, in conse- 

 quence of a belated or improper union of the parts. They are also 

 classified as internal and external, according as to whether the blood 

 escapes into a tissue or serous cavity, or actually reaches the surface of 

 the body. 



Repeated small hemorrhagic extravasations, or a single large hemor- 

 rhage, frequently result in a diminution in the volume of the circulat- 

 ing blood which must necessarily endanger the maintenance of 

 proper dynamical conditions. This vascular depression may finally 

 become so acute that the function of the different cells of the body is 

 lost completely, that of the nervous centers being affected first. 

 Hemorrhages may also prove fatal in a more direct way, in that the 

 blood may find its way into a vital structure, and render it functionally 

 useless. This is especially true of hemorrhages from the cerebral ar- 

 teries into the adjoining nervous tissue. The complex of symptoms 

 resulting therefrom, is known as apoplexy. 



Small losses of blood are readily compensated for by a temporary 

 diminution in the size of the blood-bed and a regeneration of the fluid 

 and corpuscular elements lost. The fluid portion of the blood is 

 quickly replaced by a transfer of lymph from the tissue spaces and 

 lymphatic channels. The regeneration of its corpuscular constituents, 

 however, requires a much longer time, because their formation depends 

 upon the activity of the hematopoietic tissues which is gradual and 

 cannot be made to surpass a certain maximal value. In case the 

 loss of blood has been severe, it may not be possible to effect a compen- 

 sation by ordinary physiological means, and an artificial restitution 

 of the blood lost must be resorted to. This end is accomplished by 

 the processes of infusion and transfusion. 



The former procedure purposes to replace the fluid part of the blood directly 

 by an artificial medium. A sterile 0.6 per cent, solution of sodium chlorid, heated 

 to the temperature of the body, is usually employed. If the hemorrhage has been 

 very severe and if the relaxation of the vascular system is extreme, a small amount 

 of adrenalin should be added to the infusion liquid. As this agent constricts the 

 blood-vessels, thereby lessening the size of the blood-bed, the blood pressure will 



