HUNTOON AND HUTCHISON 931 



had an immunological relationship, and that several strains or groups, while morpho- 

 logically and culturally indistinguishable, are serologically distinct. This was strik- 

 higly brought out by the work of Tunnicliff and others. 



The work of Dochez and Avery and of Havens on the group classification, of the 

 Dicks on scarlet fever streptococci, of Rivers, Amoss, and Birkhaug on streptococci 

 of erysipelas, all support the idea of distinct strains or varieties within the species. 

 Some more recent work indicates that possibly the organisms causing puerperal 

 septicemia may also form a distinct immunological group. 



One may now assume that the hemolytic streptococcus covers a number of 

 groups, each of which tends to set up a characteristic disease entity. It may be pos- 

 sible that the streptococcus under certain conditions changes its character, and then 

 tends to reproduce the same type of lesions. For example, the streptococcus of 

 erysipelas, when conditions are favorable, will continue to produce erysipelas, but this 

 does not preclude the possibility that under different conditions it may cause some of 

 the manifestations of other streptococcus infections, such as phlegmons, etc. It has 

 recently been shown capable of causing "acute anginas resembling ordinary sore 

 throat or tonsillitis without the skin manifestations of erysipelas."^ However the 

 facts may be interpreted, the tendency of the streptococcus to select certain tissues 

 and to reproduce a certain type of disease renders the problem of producing an ade- 

 quate anti-streptococcic serum for these diseases much more simple. The brilliant 

 results obtained with scarlet fever streptococcus antiserum and with erysipelas 

 streptococcus antiserum substantiate this theory. 



Preparation oj antistreptococcic serum {polyvalent). — Various methods have been used in 

 preparing anti-streptococcic serum. Space will permit only an outline of one of the more 

 recent. 



A method in common use is as follows. Cultures of the various strains used as antigens 

 arc grown in bottles containing hormone gelatin broth, and incubated until maximum growth 

 is obtained. After centrifugation the supernatant liquid or bouillon is rejected and the 

 mass of streptococci is made up into a standardized emulsion containing 50,000 million 

 organisms per cubic centimeter and heated to 55° C. for thirty minutes. This is re- 

 emulsified, and doses are prepared for the treatment of horses by mixing the emulsions of 

 different strains in proper portions. Normal full-grown horses are treated by giving intra- 

 venous injections twice a week, beginning with a dose of o.i and 0.5 cc. for the first week, two 

 doses of I cc. in the second week, and thereafter increasing the weekly doses by 2 cc. until 

 10 cc. are given at a time. This dose is repeated until trial bleedings show that the titre of the 

 serum has reached the required level. Trial bleedings are begun after the treatment has been 

 in progress four weeks and the serum is tested for agglutinins against the antigens used in its 

 preparation, and against other strains. As soon as it agglutinates all strains in a dilution of 

 1 : 200 or better, regular bleedings are made and the serum prepared and tested for sterility, 

 safety, and potency. Good sera show an agglutinin titre from i : 200 to i : 800. 



Other means of standardizing anti-streptococcic serum have been used, including a pro- 

 tection test similar to that employed for anti-pneumococcic serum, a bacteriotropin test, and 

 a complement fixation test. All of these are more or less cumbersome and apparently give no 

 better indication of the therapeutic value of the serum than the agglutination test. 



' Dick, G. F., and Dick, G. H.: J.A.M.A., 89, 1135. Oct. i, 1927. 



