Immunization. 461 



are obtained when tlie serum is injected after the toxin, but 

 before the appearance of the tetanic muscular spasms, while 

 if the injections of serum are made still later the fatal termina- 

 tion can be averted only by large doses of serum, especially 

 by its administration into the blood circulation, or directly into, 

 the brain (Roux & Borrel). After the lapse of a certain time 

 after toxin injection serum treatment is entirely without effect. 

 The protective and curative action of tetanus antitoxin 

 depends, according to the present conception, upon the fact that 

 the antitoxin molecules contained therein bind the toxin mole- 

 cules circulating in the tissue fluids and render them harmless. 

 The repeated action of the toxin on the nerve cells in the serum- 

 producing animals results in the production of excessive num- 

 bers of receptors, which are thrown off into the circulation, 

 and are therefore present in the antitoxin molecules (Ehrlich's 

 Theory, see p. 463). The serum therefore protects the nerve ele- 

 ments from the pathogenic action of the toxin molecules which 

 have not yet reached them ; but it is not capable of separating 

 toxin molecules, which have already become anchored to the 

 plasma of the nerve cells, and thereby restore the former con- 

 dition of the cells. Accordingly the serum affords protection 

 against infection immediately preceding or following its ad- 

 ministration, but if the disease has already become manifest 

 it exerts a curative action at best only, when the intoxication has 

 not greatly reduced the functional ability of the nerve cells. 



I. Immunization with Immune Serum. Such an immuniza- 

 tion is advisable and indicated in all of those cases in which 

 tetanus is feared within a short time. Such a possibility exists 

 especially after contusions which have become contaminated 

 with dirt or manure, also whenever tetanus is frequently observ- 

 ed in certain localities to follow upon certain injuries (castra- 

 tion, docking of the tail operation for umbilical hernia, skin 

 injuries, etc., and when during the operation careful asepsis 

 cannot be carried out. Where the necessary requirements for 

 a satisfactory surgical technique are present, such prophylactic 

 serum injections are of course superfluous. 



For immunization with Behring's serum large animals are injected 

 subqutaneoiisly with 20 A.-U., small animals .with 4-5 A.-U., while with 

 the. Pasteur serum 20 or 6-10 cc. respectively are used; the injections 

 may be. repeated after 10 to 12 days. The surgical treatment of the 

 wound does not become superfluous, by the use of. this serum since the in- 

 jected serum does not prevent the development of the tetanus bacilU 

 (Roux & Vaillard) . Besides the spores are retained in the wounds for a 

 long time, and if they germinate, after the disappearance of the artificial 

 'passive immunity, they produce toxins and may cause disease in the 

 animal which has again become susceptible. 



Immunization is employed to a great extent in France, in accordance with 

 Nocard's recommendations. In the period of 1895-97, 2,395 horses, asses and mules, 

 U cattle, 82 sheep and lambs, and 206 hogs were immunized. More than 2,300 



