203 



I. " Contagia are reproduced in and given off from the 

 system ; malaria is not." 



II. " Malarial fevers are not communicable from the sick 

 to the healthy." 



III. " Malarial fevers have an intermitting indefinite 

 course, and an irregular period of duration." 



IV. " An attack of malarial fever confers no immunity 

 from a second." x 



Inasmuch as each of these varieties of malarial infection 

 depends upon the intrusion of a poison from without, it is 

 not necessary for me to consider any of them in any detail. 

 In the foregoing pages (when treating of the diatheses) I 

 alluded to the nature of the malarial poison, and need there- 

 fore do no more than confine myself to the consideration of 

 how far malarial affections in general are subject to the law 

 of heredity. The diathesis due to malaria might almost be 

 regarded as universal, as few, if any, of us may be quite 

 exempt from its effects, however remote, inasmuch as from 

 the earliest times the entire human family has been brought 

 under its influence. This diathesis is also hereditary, the 

 amount of inheritance being proportionate to the intensity 

 and duration of the affection in the parents or ancestor. If 

 we remember that the subject of malaria "will display 

 through life peculiar susceptibilities," and that these effects 

 are invariably permanent, " it is easy to see that a poison so 

 persistent in its action and of which the effects, even in 

 mild cases, are so well-nigh permanent, must be capable of 

 producing that state of body which we call diathesis. The 

 malarial diathesis is, indeed, a well-marked one, and it exists 

 in greater or less degree in all who have ever come under 

 the influence of its cause." 2 Thus in the pedigree of these 

 1 Maclagan. 2 Mr. Hutchinson. 



