326 SCIENCE PROGRESS 



peas, maize meal, barley meal, etc. — may be able to attain to a higher degree of 

 fatness than ruminants, which require a certain amount of hay and straw. A lower 

 capacity for food would, of course, counteract this condition. 



DETOXICATED VACCINES (David Thomson, O.B.E., M.B., D.P.H., 

 Lecturer and Researcher on Venereal Pathology to the London Lock 

 Hospital, Dean Street, Soho). 



Our knowledge regarding immunity towards pathogenic bacteria is slowly but 

 surely progressing. It would appear, indeed, that the time is not far distant 

 when, by means of vaccines, we will be able to master perhaps the majority of the 

 infectious diseases which cause so much misery and so much loss of life amongst 

 mankind. 



It has now been definitely proved that, when a number of dead bacteria are 

 injected under the skin, a temporary inflammation is produced in the tissues, and 

 thereby these tissues manufacture a certain amount of specific antisubstances 

 towards the germs which were thus artificially introduced. These so-called anti- 

 substances, which consist of "agglutinins," "precipitins," and " bacteriolysins," 

 remain in the system for a considerable time, and by circulating in the blood they 

 render the individual less susceptible to attack by that particular germ which 

 was injected. 



All germs are more or less toxic. In some cases the toxin or poison is excreted 

 by the bacterium, but in the majority it apparently resides enclosed within the 

 germ stroma, and is known as endotoxin. Most workers maintain that anti- 

 substances cannot be successfully developed against endotoxins, so it would seem 

 logical that we should try to rid vaccines of these poisons, since they are harm- 

 ful and do not aid in immunisation. 



Emulsions of dead germs are called vaccines, and we can make a vaccine of 

 any micro-organism which we can isolate and grow artificially in pure culture. 

 Since we can now grow pure cultures of the majority of pathogenic bacteria, there 

 are in consequence a large number of different vaccines on the market. These 

 are made up of such germs as cause typhoid fever, pneumonia, influenza, bronchitis, 

 colds, meningitis, tuberculosis, puerperal fever, gonorrhoea, boils, abscesses, 

 acne, etc. • 



So far the most strikingly successful vaccine is the typhoid inoculation. It has 

 been proved beyond all doubt that an injection of 1,250,000,000 of dead typhoid 

 bacilli, followed by another injection of 2,500,000,000 ten days later, gives the 

 individual an almost certain guarantee of immunity towards typhoid fever for at 

 least one year. 



Preventative inoculations against other diseases, however, have so far been 

 much less successful, partly due to the fact that many of the germs in question are 

 too poisonous or toxic to permit of large inoculations. It is reasonable to suppose 

 that, the larger the amount of dead germs injected under the skin, the greater will 

 be the quantity of antisubstances produced against them by the subcutaneous 

 tissues. When, however, a given germ is so toxic that we dare only to inject 

 a very small amount of the vaccine, then we can hardly expect a successful 

 immunity to be produced thereby. 



In South Africa there occurs a very severe and fatal form of epidemic pneu- 

 monia amongst the negroes on the rand. In recent years attempts have been 

 made to inoculate these negroes against this disease. It was not considered safei 



