382 PHARMACEUTICAL BACTERIOLOGY 



malaria) which is introduced into the circulation by the sting of the mos- 

 quito. 



The prophylactic measures consist in the destruction of the mosquitos 

 in rooms. To this end burn two pounds of Pyrethrum to every thousand 

 cubic feet of space. Sulphur (one pound per thousand cubic feet) may be 

 used though it offers no advantage over the Pyrethrum and has the dis- 

 advantage of corroding metal and fading colored fabrics. Also destroy 

 the breeding places of the mosquito and keep mosquitos out of houses 

 by means of screens and netting. Protect the person against mosquito 

 stings when travelling in countries known to be infested by the Anopheles 

 group of mosquito. Also take quinine as a prophylactic (3 to 5 grains 

 twice daily), and as a cure. Quinine is, however, more satisfactory as a 

 preventive than as a cure. 



The life history of the malarial plasmodium is complex but it has been 

 worked out very definitely. Two life cycles are recognized, the asexual 

 (also known as the human cycle, the cycle of Golgi and the schizogonic 

 cycle), the sexual (also known as the mosquito cycle, cycle of Ross and 

 sporogonic cycle), and occasionally a third cycle known as the partheno- 

 genetic or virgin cycle, which is said to explain the latent occurrences 

 of the organism in the human body. The spindle shaped sporozoites 

 resulting from the sexual generation in the mosquito are introduced into 

 the human body by the sting of the female member of the Anopheline 

 group of mosquitoes (male mosquitoes do not bite). The leucocytes of 

 the blood devour as many of these sporozoites as they can. Those not 

 so destroyed, enter the red blood corpuscles where they undergo the signet 

 ring stage (socalled, because the stained specimens show a resemblance 

 to a signet ring) of development, finally greatly enlarging and partially 

 disintegrating the blood corpuscle by their increase in size and numbers, 

 forming the merocyte. The matured merocytes divide into a number 

 of small bodies which occur free in the blood plasm, constituting the 

 merozoites. This cycle in the human blood is completed in from twenty- 

 four to seventy-two hours, depending upon the species of malarial organ- 

 ism. Each merozoite now enters a red blood corpuscle and a similar cycle 

 repeats itself. At each sporulation a paroxysm of fever manifests itself. 

 It was found that most of the merozoites were asexual, but that some were 

 sexual. The sexual forms require longer time to mature (from eight to 

 ten days) and are known as the gametocytes. From the sporozoite intro- 

 duced by the sting of the mosquito to fully matured gametocytes (male 

 and female) constitutes the complete asexual or human cycle. The 

 gametes are now ready to enter upon the sexual cycle which can take 

 place only in the salivary glands of the female member of the Anopheline 

 group of mosquitos. The mosquito inoculates itself with gametocytes 



