462 VETEEINARY HYGIENE 



milk may be coagulated by the addition of blood serum, 

 taken from an animal into the circulation of which milk 

 has previously been injected. If the blood serum of an 

 animal be repeatedly injected into another of a different 

 species, a serum is obtained which precipitates the serum 

 of the animal which previously furnished the material, and 

 this method has been used for the detection of blood and 

 flesh of different animals. 



' Agglutinins ' and ' Precipitins ' are a third variety of 

 ' receptor ' produced by the living cells, but are distinguished 

 by having attached to their haptophore element a zymo- 

 phore or ferment group (Fig. 187) ; this latter acts through 

 the former, and produces agglutination or precipitation. 



We have now considered the three groups or Haptines of 

 lateral chains, and may present them in the form tabulated 

 by Ehrhch : 



(1) Haptines of the 



^^ . (Antitoxins. 



-Liniceptors -^ , , ,. . .... 



lAgglutmms, precipitms. 



First Order 

 (2) Haptines of the 

 Second Order 



,„, TT .• /■ ,7 (Preventive serum, 



(d) Haptines of the] , , , „ i ^ ■ 



Third Order iA"^f^oceptorslR^mo\yhc „ 



l^Cyto-toxic ,, 



2. Metchnikofs Phagocyte Theory of Immunity. — Phago- 

 cytes are certain fixed or mobile cells (leucocytes), found 

 in all the tissues of the body, which possess the power of 

 attacking, destroying, and ingesting foreign particles which 

 may enter the system. There are two kinds of phago- 

 cytes (1) Makrophac/es (mononuclear cells) which principally 

 attack cells of animal origin, and (2) Mikro2:)hages (poly- 

 nuclear cells) which are chiefly directed against bacteria. 

 The phagocyte possesses the power of engulfing the 

 living cells and completely digesting them. 



Phagocytes'are guided towards the invading matter by 

 what is known as cheviiotaxis, viz. the attraction on the 

 leucocytes of some chemical substance in the disease germs, 

 and such a condition of chemiotaxis is spoken of as j)ositive ; 



Digitized by Microsoft® 



