l86 MANUAL OF BACTERIOLOGY. 



brought about by a kind of fermentative action. So in addition 

 to the haptophore group the receptor must possess a ferment- 

 producing group. It seizes on the red cells or on the bacteria, 

 as the case may be, with the haptophore group, and produces 

 certain changes .with its ferment-producing group. The latter 

 is called the zymophore group. Receptors of this kind are 

 called receptors of the second order (Fig. 49). 



With the lysins there is also a change, which takes place after 

 the receptor unites with the bacteria or other cells; so there must 

 be here also a zymophore or zymotoxic group, as it is called. 

 This zymotoxic group, however, is not an integral part of the 

 receptor, but is easily broken off from it, in the manner described 

 below. 



As is explained later, the power of the lysins becomes sus- 

 pended, but not lost, on being heated to 55° or 56° C. In this 

 condition they are said to be inactivated. They become active 

 again when certain fresh serum is added — ^not necessarily fresh 

 lysin, but fresh normal serum. This will all be discussed and 

 explained later. For the present purpose it is sufficient to bear 

 in mind that lysin becomes inactivated and may be reactivated. 

 So the lysins act differently from agglutinins and precipitins. 

 They must have pecuhar receptors which unite, on the one hand, 

 with the cells which they disintegrate, and, on the other, with a 

 ferment-producing substance easily destroyed by heat. These 

 receptors must possess two haptophore groups; in other words, 

 a haptophore for cells and a haptophore capable of unit- 

 ing with a body containing a ferment-producing group. Re- 

 ceptors for lysins are therefore called amboceptors, or receptors 

 with two haptophores (Fig. 50). They are also called recep- 

 tors of the third order. The substance which reactivates the 

 lysin, the fresh serum, is called complement, and it must be 

 composed of a haptophore in order to attach itself to the ambo- 

 ceptor, and a zymotoxic group in order to produce lysis. On 

 heating fresh normal serum to 55° or 56° C. the complement 



