THE PROTEOLYTIC MECHANISM IN OPERATION 99 



hereditary status of the germ-plasm, is passed on to the offspring 

 of the individual. 



But ten per cent, of the individuals of each generation are not 

 able thus to ward off the attacks ; on the contrary, they suc- 

 cumb to it, and after all their tissues are devitalized to an extraor- 

 dinary degree, they ultimately die. Their failure to fight off the 

 germs is, of course, due to an inherent lack in the make-up of 

 their defensive mechanism. The mechanism in their leucocytic 

 and erythrocytic apparatus that should produce anti-ferments 

 against the tubercle germ is either altogether absent or is de- 

 vitalized and minimized in efficiency. The result is that their 

 tissues are in a condition comparable to that which the student 

 of anaphylaxis speaks of as "sensitization," and which I have 

 suggested, should be considered merely as lack of defence. Re- 

 gardless of the precise terms of the explanation, they are sus- 

 ceptible to the attacks of the germs, and this inherent sus- 

 ceptibility may be passed on to their offspring. 



It is of important, even if of incidental, interest to recall that, 

 according to the recent studies of heredity, this susceptibility 

 appears to act as a Mendelian recessive. 



That is to say, a susceptible person, mated with a normal or 

 resistant person, will have offspring that are normally resistant, 

 but who contain in their germ-plasm, as a recessive tract, the 

 factors of susceptibility or lack of immunity. If such personally 

 resistant, but potentially susceptible, individuals are mated, one 

 of their offspring in four, on the average, will be susceptible. 

 This is of great importance from the standpoint of the eugenist, 

 but need not be considered further in the present connection. 



Suffice it, for the present, that even the susceptible person is 

 susceptible only in a relative sense, and is by no means alto- 

 gether without a defensive mechanism. His chief danger may lie 

 in the fact that his cells are partially habituated to the presence 

 of this toxin, and therefore will not respond to it actively. 



If we inquire what can be done to stimulate the defensive 

 response, we are at once reminded of the methods that lead to 

 an increase of the numbers of the leucocytes in the blood. The 

 ingestion of hearty food, notably protein, leads to such increase. 

 Active exercise leads to such increase. Cold baths stimulate such 

 increase. Nourishing food in the largest quantities that can be 

 assimilated ; exercise of a fairly vigorous type, and hydrotherapy 

 would seem to be theoretically indicated. Also fatty foods to 

 conserve the protein, and iron to facilitate production of hemo- 

 globin. No practical physician needs be told that these measures 

 have been shown empirically to be of the greatest value in the 

 treatment of tuberculosis. 



Recent experiments have shown that air at very low tempera- 



