308 PARASITIC PROTOZOA IN RELATION TO THE WAR. 



length, being commonly about 12 fi or 13 /a. It is 0.25 /x broad 

 Multiplication of these parasites in the blood occurs by binary 

 lission. 



Within the gut lumen and haemocoelic or body fluid of the 

 tick, Ornithodorus moubata, the spirochretes {S. dnitoni) break 

 up into a series of minute chromatinic granules known as coccoid 

 1/odies. Some of these granules pass into the thick white Mal- 

 pighian secretion, which is voided as excrement at the end of a 

 tick's meal of human blood. The Malpighian secretion is 

 diluted with the coxal fluid, and so is able to enter the wound 

 caused by the tick bite. The coccoid bodies thus received, to- 

 gether with some sinuous forms, develop into spirochsetes in 

 man. Coccoid bodies and perhaps some spirochaetes pass with 

 the haemocoelic fluid into the ovaries of the tick, infect the ova, 

 and the young ticks are born infected, and so are capable of pro- 

 ducing infection in man when they feed. 



Spirochccta recurrentis in the louse breaks up similarly to 5". 

 ditftoni, but the mode of infection of man by way of the louse 

 diifers slightly. The irritation due to louse bites causes scratch- 

 ing and rubbing, and the lice are crushed on to the .skin. The 

 slight abrasion is quite sufficient to j^ermit the entry of the para- 

 site. Rubbing the eyes with contaminated fingers can produce 

 infection. Louse bite alone is not infective. Hereditary infec- 

 tion of lice with S. recurrentis or its varieties also occurs. 



Spirochccta icterohivmorrhagi(e. a small organism, is respon- 

 sible for the febrile condition known as Weil's disease, " infec- 

 tious jaundice " or Mediterranean yellow fever, cases of which 

 have been found on most of the war fronts. The parasite is 

 found with difficulty in the circulating blood, but is much more 

 easily recognized by examination of the livers of sub-inoculated 

 animals such as guinea-pigs. Rats may act as natural reservoirs. 

 Trench nephritis is also stated by some to be due to a spirochaete. 



Salvarsan or arseno-benzol and its modifications are effec- 

 tive in the treatment of spirocha^toses. 



Blood Sporozoa. 



The various malarial parasites are the principal .Sporozoa 

 found in the blood of man. The life-cycle of the malarial para- 

 sites is accomplished in two different hosts, man and certain 

 mosquitoes. In maiL the asexual development or multiple fis- 

 sion of the i)arasite occurs inside the red corpuscles of the blood, 

 and the succe>sive formations of asexual daughter parasites or 

 merozoites produce the attacks of fever. When the reaction of 

 man on the parasite causes the production of sexual forms, and 

 these are ingested by certain .A.nopheline mosquitos, the females 

 of which alone are aljle to suck blood, the sexual development 

 is completed in the body of the insect host, with the final pro- 

 duction of crowds of sporozoites or infective germs, that are 

 capable of infecting man. Should a parasitized female mosquito 

 suck the blood of man, tiie sporozoites are injected into the blood 



