CONCENTRATION OF IMMUNE SERA. 97 



use of serum difficult or impossible even though injection of 

 immune serum were definitely indicated. While it is true that 

 some sera are ordinarily injected at intervals of two or three 

 weeks without the production of serious results, still it frequently 

 happens that such a degree of hypersensitization to serum de- 

 velops that passive immunization must be given up entirely. 



Since the introduction of serum therapy, large numbers of 

 persons have been injected with immune serum and great bene- 

 fits have been derived from the use of different sera. The cases 

 of serum sickness, especially the rashes, have been relatively fre- 

 quent, yet are so far outweighed by the beneficial results that 

 they must not prevent the physician from the use of immune 

 sera when they are indicated. The cases of sudden death fol- 

 lowing injection of serum fortunately have been very rare. As 

 further knowledge concerning the untoward effects of the injec- 

 tion of horse serum is gained, serum disease and sudden death 

 will become less frequent. The essential points, which have so 

 far been developed, indicate, that specific sera are to be used only 

 after a definite diagnosis of the disease, that there is some danger 

 attending the injection of horse serum into asthmatics, and that 

 untoward effects of serum injections are more frequent when the 

 interval between injections ranges from ten days to several years. 



CONCENTRATION AND PURIFICATION OF SERUM. 



Frequently large amounts of specific immune substances are 

 to be injected in the treatment of infections. Hypodermic in- 

 jection of large amounts of serum, however, is painful and more 

 likely to produce serum disease, especially the rashes. These 

 objectionable features of serum therapy have resulted in an 

 attempt to produce serum of greater concentration and purity. 

 It has been found that bacteria and toxins from certain cultures 

 are more potent and cause animals to produce immune sera of 

 higher protective value. As a result virulent cultures, or toxins 

 produced by virulent cultures, have been used in active immuni- 

 zation of the animal that is to furnish the immune serum. 



Attempts have been made to obtain an increased potency by 

 separating the immune substance from the non-immune sub- 

 stance of specific serum. Dieudonne, in 1897, showed that the 

 protieds precipitated from diphtheria anti-toxin by acetic and 



