PHYSIOLOGICAL 439 



power of capturing solid particles, phagocytosis in short; and they 

 also show to a greater or less degree some power of independent 

 movement. They play a great part in the reactions of the body to 

 certain infections. They are, in early stages, the destroyers of the 

 bacilli of tuberculosis, and in later stages the chief victims of these 

 insidious intruders. They also come to form part of the tubercle 

 itself, that is to say the scar-tissue that becomes a firm nodule 

 enclosing the badly damaged tissue. They have a significant relation 

 to the virus of certain cancers, as Dr. Gye and Mr. Barnard have 

 shown; and, if transplanted from one animal to another, they may 

 start the disease afresh. In local inflammations they act as 

 scavengers, and, on the other hand, they may in such cases help in 

 the formation of new tissue, replacing what has been destroyed. 



In conditions of health, the histiocytes play a great part in the 

 destruction of red blood corpuscles which is always going on, for 

 these important cells have but a short life. It follows from this 

 connection that the activity of the reticulo-endothehal system has 

 something to do with cases of pernicious anaemia, where a normal 

 balance of repair and waste is disturbed by a destructiveness that 

 runs riot. Lastly, it is becoming clear that the histiocytes are inti- 

 mately associated with another of the body's internal defences, 

 namely, the production of "anti-bodies", which demand a paragraph 

 to themselves. 



ANTI-BODIES OR ANTI-TOXINS.— This is a convenient term 

 for specific chemical substances which serve to neutralise specific 

 poisons or toxins. They might also be called counteractives. Roux and 

 Yersin discovered the toxins of microbes; Behring and Yersin 

 demonstrated the reality of anti-toxins; Roux and Martin showed 

 how specific anti-toxins might be produced by introducing a specific 

 microbe into the blood of some animal, such as the horse, and then 

 used for injection into man (or some domesticated animal) in 

 anticipation of, or even subsequent to, an infection with the virulent 

 microbe in question. Lest man's native powers of producing anti- 

 toxin for himself should be inadequate as regards the amount 

 produced or as regards rapidity of production, he may receive 

 extraneous assistance. The value of the injected anti- toxin that 

 works against the rapidly poisonous secretion of the diphtheria 

 microbe is attested by the number of children whose life it has saved. 

 Even against snake-poison, which is non-microbic, an extraneous 

 anti-toxin may be successful. Snake-poisons are proteins, and it is 

 against strange proteins, such as those secreted by virulent bacteria- 

 that anti- toxins work. 



It should be noted here that no one has as yet succeeded in isolating 

 an anti-toxin; what is injected is a serum-preparation, including the 

 anti- toxin. It is not indeed certain that anti- toxins are definite 



