230 BACTERIA PATHOGENIC TO MAN 



ducing the poison into the subarachnoid space, owing to the passage 

 of the poison into the blood, there is a general poisoning and not a 

 cerebral tetanus. This at least is the case if care has been taken during 

 the operation to avoid injuring the brain mechanically. 



If now we follow the course of the antitoxin in the organism as 

 we have just done with the toxin, we find that: whereas the toxin 

 passes directly to the nerve paths, the antitoxin when injected sub- 

 cutaneously is entirely taken up by the blood-vessels by means of the 

 lymph- vessels. From the blood it then reaches the tissues, with the 

 fluids of which it mixes. 



The complete absorption of a given quantity of antitoxin adminis- 

 tered subcutaneously takes place rather slowly. In his animal experi- 

 ments Knorr found the maximum quantity in the blood only after 

 twenty-four to forty hours. From that time on the amount again 

 steadily decreased, so that by the sixth day only one-third the optimum 

 quantity was present. By the twelfth day only one-fiftieth and at the 

 end of three weeks no antitoxin whatever could be demonstrated. 



Naturally the time during which these changes take place varies 

 with the application, the conditions of absorption, and the concentra- 

 tion and amount of the preparation injected. When injected intra- 

 venously the antitoxin very quickly passes into the lymph. Ransom 

 was able to demonstrate it in the thoracic duct of a dog a few minutes 

 after intravenous injection. Neither the central nervous system nor the 

 peripheral nervous tissue take up any antitoxin from the blood. Only 

 after very massive intravenous doses are small traces found in the 

 cerebrospinal fluid. From this it is at once clear that passively and 

 actively immunized animals become tetanic if the poison is injected 

 directly into the central nervous system or into a peripheral nerve. 

 Antitoxin injected subdurally also passes almost entirely over into the 

 blood. 



A rapid and plentiful appearance of antitoxin in the blood is depend- 

 ent on the content of serum in antitoxin units. The more units, the 

 more rapidly will the blood develop a high content of antitoxin; and 

 the higher this is the more thoroughly will the tissues be saturated with 

 the antitoxin. 



From the foregoing it is not difficult to formulate the conditions 

 under which an antitoxin introduced into the organism can exert its 

 neutralizing power on the toxin. We see that the poison deposited at 

 any given place takes either of two paths to the central nervous system, 

 one a direct path by way of the local peripheral nerves and the other 

 an indirect path through the lymph channels and blood to the end 

 plates of all other motor nerves. From intact bloodvessels the anti- 

 toxin penetrates neither the substance of the peripheral nerves nor 

 the substance of the central nervous system. Hence, only that portion 

 can be neutralized which (a) still lies unabsorbed at the site of inocula- 

 tion, or (6) which, though it has passed into the blood, has not yet been 

 taken up by the motor-nerve endings. A curative effect can therefore 

 result from antitoxin introduced subcutaneously or intravenously only 



