1895.] on the Antitoxic Serum Treatment of Diphtheria. 439 



drawn from the vessels, separates very perfectly into two portions — 

 a firm clot, which if the blood be caught in a cylindrical glass jar, 

 forms a kind of column in the centre, and a clear straw-coloured 

 serum which accumulates around the clot, and forms a layer often 

 several inches deep above it. [Illustration shown.] This serum con- 

 tains the antitoxic substances. Lastly, considerable quantities of 

 blood can be obtained from such a large animal as the horse, and if 

 he be well fed, groomed and exercised, the process of bleeding may 

 be repeated pretty frequently without causing any inconvenience to 

 the animal : in fact, he stands bleeding as well as did our forefathers, 

 who thought as little of being bled as we think of going to Aix or 

 Buxton. 



Let us now turn for a moment to the method of treating the horses 

 that we wish to render immune, in order that they may supply the 

 antitoxic serum that is to be used for the treatment of cases of 

 diphtheria. Eoux's method, which is that that has been most care- 

 fully described, and which is the one used in this country first by 

 Dr. Ruffer at the British Institute of Preventive Medicine, and then 

 by Professor McFadyean at the Eoyal Veterinary College, consists 

 in introducing diphtheria toxine of a given strength in gradually 

 increasing doses, until the blood of the animal so injected is found 

 to contain a sufficient quantity of the antitoxine. 



The toxine with which the animal is to be injected is made as 

 follows : — A broth is prepared by soaking a pound of finely-minced 

 beef in water. This is allowed to stand for twenty-four hours in the 

 cold. To the fluid expressed from the meat fibre at the end of that 

 time is added J per cent, of common salt and 2 per cent, of peptone 

 (meat artificially digested by pepsine). This broth is then rendered 

 faintly alkaline by the addition of soda salts or caustic soda. This 

 is done because it is found that the diphtheria bacillus cannot grow 

 at all vigorously, or form its poisons rapidly in an acid solution, and 

 such poison as is formed is neutralised, or is unable to act in the pre- 

 sence of even a faint trace of acid. It is found that even in Eoux's 

 solution, which is always faintly alkaline to begin with, an acid 

 reaction soon appears, but, after about ten days, this is replaced by 

 an alkaline reaction, and as soon as this takes place, the growth of 

 the bacilli takes on new activity, the quantity of toxine is increased, 

 and it becomes much more virulent. Eoux found that he obtained 

 his most virulent toxines after three weeks' or a month's growth. If 

 the growth is allowed to go on longer than this, a process of oxida- 

 tion appears to take place, and I have found that the toxine from a 

 culture carried on for two months had already lost much of its toxic 

 activity. It should be noted that a virulent bacillus should always 

 be taken in the first instance, otherwise the results may be very 

 disappointing. 



This nutrient broth is placed in a layer of not more than half an 

 inch thick in a flat-bottomed flask, which is plugged with cotton wad- 

 ding, and then closed with an indiarubber cork or cap. [Illustration 



2 h 2 



