THE MANUFACTURE AND USE OF SERA AND VACCINES. 1 29 



is a brief outline of the manufacture of the marvelous remedy for the treat- 

 ment of the dread disease of childhood, namely diptheria. 



3. Antidiphtheric Serum. 



A. Selecting and Testing the Horse. — Ordinary, normal, non-pedigree 

 horses are preferred, purchased under a guarantee of soundness. Even 

 though purchased under such a guarantee the animal is kept under observa- 

 tion for a few weeks and tested for glanders by the mallein test. No animal 

 is retained until it is proven that there is no latent or active disease present. 

 The animal is well housed and well cared for during the entire time, under 

 conditions as sanitary as it is possible to make them. All laboratories are 

 also regularly visited by a U. S. Government inspector, who reports his find- 

 ings to Washington. 



B. Preparing the Toxin of Diphtheria. — Pure cultures of a breed or 

 strand of the diptheria bacillus, possessed of a high potency, virulency or 

 toxicity, are made in liter flasks containing beef bouillon. The original ba- 

 cilli thus used are taken from some patient suffering with diptheria, and by 

 means of isolation methods all foreign microbes are rejected or excluded. 

 After the culture is several days old or when a maximum amount of the toxin 

 has been formed and deposited in the boviillon, the bacilli are killed by adding 

 0.25 per cent, of trikresol. The bouillon with the dead bacilli is filtered. 

 The clear filtered substance constitutes the toxin which is injected into the 

 horse for the purpose of developing (in the horse) the antitoxin of diptheria. 

 The virulency or potency of the toxin varies and is tested on guinea-pigs and 

 compared with the U. S. Government standard. The desirable breed, race 

 or strain of germs is perpetuated in the laboratory by daily transfers to new 

 culture tubes. In this manner the bacilli are maintained for a long time, 

 several years or longer. However, even with the greatest care the race finally 

 deteriorates, weakens or undergoes a change in potency and it becomes 

 necessary to secure a new stock culture. 



C. Developing the Antitoxin of Diptheria in the Horse. — Twice weekly 

 the horse is given (by hypodermic injection into the flank region) gradually 

 increasing doses of the toxin of diphtheria. The rule is to give enough to 

 produce a marked reaction. For a day or two the horse is sick with diph- 

 theria, then recovers as the increased antitoxin in the blood (serum) of the 

 animal neutralizes the toxin. This is continued for from four to six weeks 

 when a maximum amount of antitoxin has presumably developed. The 

 last dose of toxin is several hundred times greater than the first. 



D. Bleeding the Horse. — A sterilized canula or trochar is inserted into 

 the jugular vein, after the neck has been thoroughly washed with soap and 

 water, shaved and rinsed with a 5 per cent, solution of carbolic acid. The 



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