448 MATERIA MEDIC A AND THERAPEUTICS. 



etc., or as highly complex compounds. It is most important, 

 however, for the student to observe that, beyond the alkalies 

 and acids, but few drugs act upon the plasma. The great 

 majority of them simply exist in it, and are conveyed by it 

 to the tissues and organs of elimination, where they exert their 

 specific influence. 



But we may go beyond this, and alter the total amount 

 of blood or plasma in the body by actually adding to it from 

 the blood of another person or animal. This is done by trans- 

 fusion, a powerful means of restoring the blood, but one which 

 is not always readily available. 



2. "We can affect the value of the plasma through the ex- 

 penditure or egesta. "We have seen that purgation is a ready 

 means of influencing the water, salts, albumen, and other con- 

 stituents of the plasma in the portal system, and thus in the 

 blood generally. "We shall find in subsequent chapters that in 

 the same way we can stimulate excretion by the kidneys and by 

 the skin. We shall also discover, under the head of metabolism, 

 that we can so far either tax or spare the great organs which 

 are the source of vital energy and therefore of waste, such 

 as the muscles, and thus the metabolic and nutritive value of 

 the whole blood. But we can go much farther than this: we can 

 actually abstract a certain quantity of blood by venesection, 

 cupping, or leeching, as we have already seen in the case of the 

 portal vein ; and such alteration in quantity will cause a decided 

 alteration in quality, for, as we shall find in chapter x., ab- 

 straction of blood increases the amount of water in the 

 plasma. 



3. A small number of drugs are known to act directly upon 

 the white corpuscles. Quinia reduces their number, and paralyses 

 their movements ; Veratria kills them (out of the body). All 

 aromatic oils, resins, and gum-resins, especially Myrrh, are 

 believed to increase their production. 



4. We can increase the richness of the blood in red corpuscles , 

 and the richness of the individual corpuscles in haemoglobin, by 

 giving abundant digestible and assimilable food, and by secur- 

 ing the activity of the lacteal tract, which is concerned in their 

 production. Fresh air and sunlight can be secured by change 

 of habits or residence. We can also increase the constituents 

 of the red corpuscles admitted into the system. Iron, which the 

 pharmacopeia provides in so many forms, directly increases the 

 amount of haemoglobin even in healthy individuals. Carbonate of 

 Potash, in proper combination with Iron, as in the Mistura Ferri 

 Composia or Blaud's pill, unquestionably increases its value. 

 Phosphoric Acid, whether as the Diluted Acid or as the Phosphate 

 of Iron and other bases, is also a reputed blood-restorer. All 



