THERAPEUTIC APPLICATION OF ANTITOXIN 435 



therefore, the most suitable animal and is usually employed. 

 The serum is now standardised by a method similar to that set 

 up for diphtheria antitoxin (see Chapter XXIL), and its strength 

 is reckoned in terms of similar units. In ( this country the unit 

 ■ordinarily used is that determined by the method practised in 

 the U.S.A., and the sera contain from 150 to 800 units per c.c. 

 Sera maintain their potency for a considerable period, but a serum 

 more than a year old should not be used unless it has been 

 subjected to fresh standardisation. Sera should always be stored 

 in a dark and cool place. 



The essential factors for the success of serum therapy are, 

 first, that there should not be an hour of unnecessary delay in 

 commencing treatment after a case is seen, and secondly, that 

 the antitoxin should be given in proper amount. There are four 

 paths .by which the serum may be given, namely, subcutaneously, 

 intramuscularly, intravenously, and intrathecal!}' by lumbar 

 puncture. The disadvantage of the first two methods is that 

 absorption is relatively slow — of the latter, that elimination is 

 relatively rapid. The earlier injections ought therefore to be 

 given either intravenously or intrathecally, and some difference 

 of opinion exists as to the relative merits of the two routes. 

 The chief advantage of the former is that large quantities of the 

 remedial agent can be quickly administered, and Henderson 

 Smith has shown that a high concentration of antitoxin in the 

 body fluids is maintained for a considerable time ; the neutralisa- 

 tion of toxin passing out from a focus of infection is thus 

 facilitated. The argument in favour of the intrathecal method 

 is that the serum thereby gains rapid access to the grey matter 

 of the cord on which the toxin is exerting its specific action. In 

 the absence of definite experimental evidence, the effects of 

 treatment by the two methods can only be judged of by the 

 clinical results and, up to the present, data for a final decision 

 are not available. The War Office Committee officially re- 

 commends that the first injections should be given by the 

 intrathecal method and the later by intramuscular and sub- 

 cutaneous routes, the principle being that, as the antitoxin first 

 given is eliminated, its place is taken by the more slowly 

 absorbed and therefore more gradually eliminated moieties. 



For the earlier injections — intrathecal or intravenous — the 

 patient must be put under a general anaesthetic. The intra- 

 thecal injection is practised by making an ordinary lumbar 

 puncture and withdrawing 20 c.c. of cerebro-spinal fluid. A 

 corresponding amount of antitoxin, warmed to the body tempera- 

 ture, is then slowly introduced, the pulse and respiration being 



