442 Dr. G. Sims Woodhead [Feb. 8, 



dose of diphtheria toxine, and in a test-tube adds a definite and 

 known quantity of the blood to be tested. This mixture is then 

 injected into a guinea-pig, and if the antitoxic power of the blood 

 has been gauged aright, the animal does not suffer in the slightest 

 degree from what under ordinary circumstances would kill ten 

 guinea-pigs. The addition of less or weaker serum, or of more 

 toxine, would leave the mixture still toxic. 



In order to obtain a definite standard with w T hich to compare the 

 antitoxic power of any serum, and to determine the dose of such 

 serum, Behring and Ehrlich have described what they term a normal 

 antitoxic serum — that is, a serum of such a strength that y 1 ^ of a 

 c.c. added to ten times the lethal dose of diphtheria toxine is exactly 

 sufficient to render it innocuous, 1 c.c. of such normal serum contains 

 one " immunisation unit," and should be sufficient, when added to a 

 hundred times the lethal dose and injected, to render it innocuous. 

 In horses w 7 holly immunised the serum may be fifty or even a hundred 

 times as active as the normal serum above mentioned, and the dose 

 to be given varies according to the number of immunisation units in 

 any sample. It is not here necessary to go into the question of dose, 

 but it may be stated that 500 of these immunisation units are usually 

 necessary to produce the desired effects in cases of diphtheria, though 

 in some cases still larger quantities have to be used. Behring now 

 supplies four strengths of the serum, the weakest (marked with a 

 yellow label) is sent out for injection of cases where the disease has 

 not already been contracted. The next (marked with a green label) 

 is of a strength of 600 antitoxine units, and is given to those cases 

 in which the treatment is commenced at the very outset of the disease 

 — that is, when the first symptoms of diphtheria manifest themselves. 

 The next stronger antitoxic serum (white label) equals 1000 anti- 

 toxine units, and is used for cases somewhat more advanced in which 

 the prognosis is at all grave ; whilst in still graver cases, and where 

 the symptoms have been developed for some considerable time, it is 

 often necessary to give a serum of 1500 units ; this is marked with a 

 red label, and is, of course, highly concentrated in order that the size 

 of the dose may not be unduly increased. In place of No. 1, healthy 

 children and adults who are exposed to diphtheritic infection may 

 receive a quarter of the dose of the green label flask, which Behring 

 considers will protect against diphtheria with very great certainty. 

 Although these general directions are laid down, it is strongly 

 insisted upon by Behring, Kossel, Boux, and in fact by all those 

 who have had experience of antitoxic serum, that the dose must vary 

 according to the severity of the disease, so that much must be left to 

 the discretion of the medical practitioner in charge of the patient. 

 The great error into which those who first use this agent fall, is the 

 administration of far too small a dose, especially in the case of 

 children, for whom the dose is nearly as large as it is for adults. 

 For this reason some of the statistics published in this country and 

 abroad are far too unfavourable to the method. The great drawback 



