ANTITOXINS AND. SERUM THERAPY. 59 



toxin immediately before the injection is mixed with i of its 

 volume of Gram's solution. This is used for several weeks, and 

 afterwards only pvire toxin is injected. 



The horses employed for this purpose are animals no longer fit 

 for work, and it is necessaiy to inject them first of all with mallein 

 to be sure that they are not suffering from glanders. 



In a horse inoculated by Roux, the injection began with | cc. 

 of iodised toxin, increased to 1 cc. by the thirteenth day, and the 

 injection continued daily. On the seventeenth day \ cc. of pure 

 toxin was injected, and this was increased by the forty-first day 

 to 10 cc. ; and on the forty-third day 30 cc. of pure toxin were 

 injected, causing pronounced oedema. The doses were still further 

 increased, untU on the eightieth day 250 cc. were injected. In 

 two months and twenty days the horse had received 800 cc. of 

 toxin. 



On the eighty-seventh day the serum obtained had an immunising 

 power of over 50,000. By this is meant that a guinea-pig resisted 

 inoculation of j cc. of virulent diphtheria culture when injected 

 twelve hours beforehand with serum in quantity equal to the -gxjwff 

 part of its body weight. 



There are two tests which can be appKed to the serum. Pirst, 

 the antitoxic serum added to diphtheria toxin rendei'S it inert ; and, 

 secondly, if serum is injected into a guinea-pig and toxin injected 

 several hours afterwards, no result follows. 



Several ways have been suggested for estimating the ' immunising 

 power of the serum. , 



In Ehrlich's system, the unit is represented by '1 cc. of anti- 

 toxic serum, which, added to '8 cc. toxin, will neutralise it so that 

 the whole may be injected subcutaneously in a guinea-pig without 

 producing cedema. The standard toxin is a toxin of which -3 cc. 

 is fatal to 1 kilo, of guinea-pig. 



But the preventive power of the serum is best expressed by the 

 result of a subsequent injection of toxin. The immunising power is 

 estimated by the number of grammes of guinea-pig which can be 

 protected against the minimum fatal dose of toxin by 1 cc. of anti- 

 toxic serum. 



The antitoxic serum can be kept in sterilised flasks in the dark, 

 with the addition of a small piece of camphor, or it may be dried 

 in vacuo, powdered, and thus supplied in a convenient form for trans- 

 port. It has n>prely to be dissolved in water before use. 



Klein employed a modified plan by which he claimed to have 

 obtained antitoxin in afar shorter time i than is possible by Roux's 



