DIPHTHERIA 99 



fore, called diphtheria antito.vin. At the present time 

 this diphtheria antitoxin is made by injecting horses 

 with gradually increasing' doses of diphtheria toxin over 

 a period of several months, until at last the horse will 

 stand, at one injection, as much diphtheria toxin as 

 would ordinarily suffice to kill several hundred horses. 

 Then the animal is bled, as much as ten quarts of blood 

 being sometimes collected at one bleeding. When this 

 blood is allowed to stand in a sterile vessel, in a cool 

 place, it clots, and a clear, Hght-yellow fluid separates. 

 This fluid is the blood-scrum, and constitutes the 

 diphtheria antitoxic serum used in the treatment of 

 the disease. It is necessary to carefully test this anti- 

 toxic serum for purity and also for its strength. The 

 latter is indicated by finding out against how many 

 fatal doses of toxin a certain quantity of the serum will 

 protect an animal. This is expressed by saying the 

 serum contains so many units per cubic centimeter.^ 

 The ordinary sera now on the market contain from 500 

 to 1500. units per cubic centimeter. 



In the treatment of diphtheria the antitoxic serum 

 should be given early and in full doses (from 3000 to 

 10,000 units, depending on the severity of the disease). 

 Ordinarily the serum is given by means of hy[)odcrmic 

 injections, but in severe cases, especially when seen late, 

 it is well to make the injections directly into a vein. 

 When there are several children in the family affected, 

 injections may also be given to the well children, in 

 order to prevent their contracting the disease. Such 



1 As a matter of fact, one unit is that amount of antitoxin which 

 will just protect a guinea-pig against 100 fatal closes of diphtheria 

 toxin. 



