57 
In the former instance we have to deal with cumulative infection, 
taking place week after week and year after year, hence siicc(‘ssive 
generations of parasites come into consideration. 
In the latter instance we have to deal with the individual life of the 
parasites which are present in the patient at the time he leaves the 
infested area. 
A failure on the part of most observers to distinguish betwetui th(‘S(* 
two classes of cases renders the published data less valuable than thev 
otherwise would be in determining the duration of uncinariasis. 
In my own observations, I have found people remaining in the 
infested areas who gave a history of the disease e.xtending bac*k for 
ten, twelve, and even tifteen }’ears. I have further tlm‘e observations 
which I consider free from criticism in connection with j)atients who 
presented the disease six years (2 cases) and even six years and seven 
months (1 case) after being removed from the source of infection. I 
also have one observation, which is not free from criticism, upon a 
patient who showed the disease ten years after entering a hos])ital. 
Sandwith (1894, p. 15) in discussing the duration of illness says — 
“Nearly every patient said he had been ill two or three years l>efore adniiR>^ion. 
I find among my notes 29 cases, uncomplicated by other diseases, whert* the jiatient^ 
said they had suffered more than three years. Of these, 13 had been ill for font 
years, 6 for five years, 3 for six years, 2 for eight years, 2 for nine years, 2 for eleven 
years, and one vowed it was fifteen years since the commencement of his symptoms. 
“It may be safely said that during these long intervals of time very few i)atient.>j 
had any rational treatment.” 
It is probable that 
infections. 
Sandwith's cases were 
subject to cumulativi' 
LENGTH OF LIFE OF THE INDIVIDC.VL PA KASITl->. 
It is already established that for every hookworm which is jiresent 
in the intestine a separate embryo must entiu* the body. In oth(‘r 
words, the eggs which the female worm d(*posits in the intestine will 
not develop there to mature parasites, but must first 1 m‘ discharged in 
the feces and undergo certain changes. 
It is further clear that direct autoinfection, such as takes place in 
the case of jiinworms {O.rytu'ts rermicnhtrix). is excludml. hor 
instance, suppose a child is at stool and .soils his tingiu-s with the 
feces, which contain hookworm eggs, tlnm puts his lingers into his 
mouth and swallows the eggs; the.si* ova will not develop in the 
bowels into adult worms. 
Whether an Unchuiria egg, which happ<me<l to get un(h‘r the linger 
nails, could reach the larval infecting stagi* in that jilace i.^ jierhajis an 
open (jue.stion. So far as I am aware, the point ha^* n ver Immmi 
studied, but what is already known about this group of jiane-ites does 
not lead me to believe that such a condition would be es|M‘cially 
common, although it does not semn ab.solutcdy impossibh*. 
