IMMUNITY AND SUSCEPHBILITY 699 



lowing way; the antigenous substances combine with the cells utilizing 

 all the available receptors, leaving none open for food and thus pervert- 

 ing the general metabolism of the cell. In such cases there is a regener- 

 ation 6f these chemical receptors by the tissue cells which more than 

 compensates for those with which the antigen has combined and as 

 a result the cell discharges them (chemical substances) free into he 

 body fluids. 



The various antibodies are usually produced with more avidity 

 by certain tissues than by others. Antibody formation may be of a 

 strictly local character depending upon the point where the antigen is 

 injected. For example, when abrin is placed in the eye, antiabrin is 

 produced, but only in the eye so injected. In the majority of cases the 

 antibodies are produced in some special tissue or tissues at a distance 

 from the point of injection. 



Following the injection of an antigen into the body of an animal 

 there is always a decrease in the resistance of that body and a decrease 

 in the antibodies produced followed in a short time by a marked increase 

 in their formation. The former condition is spoken of as the "negative 

 phase" and the latter as the "positive phase." 



Antibodies may be transferred from mother to young before birth, 

 but only after fetal circulation is established. It has been positively 

 demonstrated that antibodies are not transferred by the ovum or the 

 spermatozoon directly. They are only carried from the blood of the 

 mother and diffused through the placenta into the blood of the fetus. 

 It has, however, been shown that the eggs of immunized chickens con- 

 tain antibodies occasionally. This is "germ-cell transmission" and 

 not true hereditary transmission. The transferred immunity or anti- 

 bodies do not remain over two or three months in the bodies of the 

 offspring after birth. 



Antitoxins. — ^Antitoxins are so called because they combine with 

 and render inert the soluble toxins. Antitoxins are produced for all 

 the bacteria producing soluble toxins and for the toxic substances of a 

 large number of other plant and animal cells. Antitoxins are the free 

 chemical receptors of certain of the cells of the body. That is, they are 

 chemical substances which have been thrown off from the cells of the 

 body and in all probability were normally used for the purpose of taking 

 up food substances. These chemical substances are produced in excess 

 of those actually needed by the cell due to a stimulation of the cells by 



