THE PATHOGENIC PROTOZOA 149 



transmission by the general circulation through the blood, i.e., 

 through the placenta ; and further, spirochaetes have been seen 

 in the interior of the ova in female congenital syphilitics ; it is 

 not known with absolute certainty whether, and how, a spirochaete 

 passes from the general circulation of the mother, or from the 

 spermatic fluid of the father, into the ovum which after fertilisa- 

 tion is to produce an embryo infected from the start, whose 

 life in consequence will be more or less soon cut short. But 

 taking all the facts we know we have almost a complete 

 demonstration of true inheritance. 



Protozoal disease and hereditary disease are two terms so 

 closely associated in our minds to-day that the protozoal nature 

 of the spirochaete is invoked to support the hereditary character 

 of syphilis, and this latter is brought forward as an argument 

 in favour of the protozoal nature of the spirochaete : there are 

 at the base of this somewhat easy-going argument facts which 

 are sufficiently certain. 



The striking analogies between syphilis, a spirochaete infection, 

 and sleeping sickness, a trypanosome infection permit of the 

 belief that the spirochaete of Schaudinn is a protozoon. Among 

 the more or less late complications of syphilis are locomotor 

 ataxy and general paralysis. Now there is also known an 

 ataxic condition in dogs infected with trypanosomes 

 (Spielmeyer's experiments), and there exists a general paralysis 

 with all the mental stigmata of that disease in men attacked by 

 sleeping sickness (G. Martin and Ringenbach). 



There are doubtless more protozoal diseases than we think 

 to-day, and it may quite well be that protozoa are the cause of 

 those infections whose nature is still unknown e.g., yellow 

 fever, cattle-plague, and the horse-sickness of the Transvaal. 

 Yellow fever in particular is transmitted by a mosquito 

 (Stegomyia fasciata\ which does not infect until after the 

 1 2th day from the time at which it was itself infected. The 

 individual bitten passes through a period of prostration which 

 lasts three to five days, and at this moment his blood becomes 

 infective for the mosquito, but only for a period of three days ; 

 these facts indicate a life-cycle in the mosquito and in man, 



