VACCINE THERAPY IN THEORY AND PRACTICE 603 



injected in gradually increasing doses into a sheep, the sheep's 

 serum develops " erythrocytotropic " or " haemolytic " sub- 

 stances, which dissolve goat's corpuscles, so that if this serum 

 be mixed with goat's corpuscles they become dissolved and 

 a clear solution of haemoglobin is obtained. The serum will 

 only cause haemolysis of sheep's corpuscles, or those of some 

 species nearly allied : this is important, as it is an instance of 

 the specific nature of anti-bodies. 1 



If milk be injected into an animal in progressive doses, 

 its serum develops " galactotropic " substances which coagulate 

 milk, and the injection of spermatozoa or of ciliated epithelium 

 leads to formation of anti-bodies in the serum which arrest the 

 movements of these cells. The formation of anti-toxins to the 

 toxins of diphtheria and tetanus has been referred to ; they are 

 developed after injection of the toxins in progressive doses into 

 horses, whose serum is drawn off and standardised. This is so 

 well established as to be a matter of commercial enterprise. 



This property of the blood of forming anti-bodies is the 

 explanation of the phenomenon of recovery from disease. 

 Virulent bacteria are introduced, and gradually the blood lorms 

 bacteriotropic substances which exercise some hostile influence 

 over the bacteria. The object of vaccine therapy is to stimulate 

 the blood to form anti-bodies to a given bacterium by injection 

 of the same organisms in a dead condition, and so incapable of 

 further infecting the patient. 



The rationale of this as a prophylactic measure, to provide 

 a person with a given set of anti-bodies before exposure to 

 infection, is easily understood. Curative inoculation requires 

 some further consideration. The obvious criticism is that it 

 must be useless to introduce more organisms, dead or alive, 

 when the body already contains more than it can deal with. 



The reasons for curative inoculation come out ot the 

 following considerations. Bacterial infections are of two kinds 

 — general, or septicaemic, and local. In the septicaemias the 

 organisms are in circulation in the blood, and may sometimes 

 be cultivated from it ; but in local infections the bacteria are 

 confined in certain areas, such as one or more joints or glands, 

 and none can be recovered from blood cultures. The local 

 infections are those which give the best results from vaccine 

 therapy, and this is because in these cases the circulating 



1 Macleod, in Recent Advances in Physiology and Biochemistry. 



