128 ANTITOXINS. 



needle carefully introduced into the subcutaneous tissues. As 

 the injection is made the needle is withdrawn slowly and 

 gradually, and the opening sealed with collodion. Slight 

 manipulation of the part will facilitate absorption of the serum. 



Many of the ill-(ffects following the administration of 

 antitoxin are due to careless technique and lack of suffi- 

 cient cleanliness. Localized suppuration, septicaemia, and 

 pyaemia are quite likely to follow careless injection. The 

 patient should be absolutely quiet while the injection is made, 

 so that the needle of the syringe will not penetrate any further 

 than into the subcutaneous tissues. In the case of children, 

 it is best to wrap them in a sheet or large cloth, leaving only 

 the site of injection exposed. The child is held firmly by an 

 assistant to prevent its struggling. 



Immunization : Immunization is the process of rendering 

 immune. It usually implies forced immunity or the gradual 

 production of immunity by the repeated injection of carefully 

 graded doses of toxin. Any animal may be used for this 

 purpose, but some large animal, like the horse, is preferable, 

 because a larger amount of blood can be withdrawn at one 

 time. The animal must be free from tuberculosis or glanders 

 or any other infectious disease, and should be kept in a clean, 

 aseptic stable, and be well cared for. Living cultures, attenu- 

 ated cultures, dead cultures, filtered cultures, or the toxin, are 

 used for this purpose. 



The animal is injected first with a very small dose of the 

 substance used, in order to ascertain its susceptibility to the 

 poison. After it has recovered from the effects of this first 

 injection a larger dose is given. This is repeated at intervals 

 until the animal shows no reaction whatever to hundreds of 

 times the original, fatal dose. This indicates a condition of 

 tolerance, or what might be termed a toxin-habit, and results 

 in a very high degree of immunity. The immunization must 

 be carried on judiciously. Care must be taken not to exhaust 

 the tolerance of the animal, as a condition of hypersensitivity 

 may be produced to which the animal usually succumbs. 

 There is, in short, a limit to the tolerance of the animal, 

 and this limit must not be passed. The serum of highly 

 immunized horses is most suitable for therapeutic purposes. 



