THE BLOOD. 167 



The process is retarded by a low temperature, addition of 

 abundance of neutral salts, extract of the mouth of the leech, 

 peptone, much water, alkalies, and many other substances. 

 The excess of carbonic anhydride and diminution of oxygen 

 seem to be the cause of the slower coagulation of venous blood, ' 

 hence the blood long remains fluid in animals asphyxiated. A 

 little reflection suffices to explain the action of most of the fac- 

 tors enumerated. Any cause which hastens the disintegration 

 of the blood-cells must accelerate coagulation ; chemical changes 

 underlie the changes in this as in all other cases of vital action. 

 Slowing of the blood-stream to any appreciable extent likewise 

 favors clotting, hence the explanation of the success of the 

 treatment of aneurisms by pressure. It is plain that in all 

 such cases the normal relations between the blood and the tis- 

 sues are disturbed, and, when this reaches a certain point, 

 death (coagulation) ensues, as with any other tissue. 



Clinical and Pathological— The changes in the blood that 

 characterize certain abnormal states are highly instructive. If 

 blood from an animal be injected into the veins of one of an- 

 other species, the death of the latter often results, owing to non- 

 adaptation of the blood already in the vessels, and to the tissues 

 of the creature generally. The corpuscles break up — the change 

 of conditions has been too great. Deficiency in the quantity of 

 the blood as a whole (pligoBmia) causes serious change in the 

 functions of the body ; but that a haemorrhage of considerable 

 extent can be so quickly recovered from speaks much for the 

 recuperative power of the blood-forming tissues. Various kinds 

 of disturbances in these blood-forming organs result in either 

 deficiency or excess of the blood-cells, and in some cases the 

 appearance of unusual forms of corpuscles. 



Ancemia may arise from a deficiency either in the numbers 

 or the quality of the red cells ; they may be too few, deficient 

 in size, or lacking in the normal quantity of hsemoglobin. In 

 one form (pernicious anoBmia), which often proves fatal in 

 man a variety of forms in the red blood-cells may appear in the 

 blood-stream ; some may be very small, some larger than usual, 

 others nucleated, etc. Again, the white cells may be so multi- 

 plied that the blood may bear in extreme cases a resemblance 

 to milk. 



In these cases there has been found associated an unusual 

 condition of the bone-marrow, the lymphatic glands, the spleen, 

 and, some have thought, of other parts. 



