160 REPORT OF THE HARVARD AFRICAN EXPEDITION 
made up with human blood serum and their salivary glands dissected and teased 
up in the solution. One cubic centimeter of this solution containing many 
sporozoites was then drawn into a hypodermic syringe, allowed to remain for 
fifteen minutes and then injected intravenously into a patient. On the tenth 
day following inoculation the patient had a malarial paroxysm, the tempera- 
ture rising to 103.6° F., and Plasmodium vivax was found in the blood. This 
experiment suggests that the sporozoites of Plasmodium vivax when exposed 
for fifteen minutes to a concentration of quinine equal to fifteen grains in the 
human being are not injured so far as infectivity is concerned, and that this 
dosage in prophylaxis is not sufficient to prevent infection. Several investi- 
gators have shown that infection with malaria sometimes occurs, even though 
the victim is taking as much as fifteen grains of quinine a day for prophylaxis. 
Yorke and Macfie! in their work upon the treatment of general paresis of the 
insane by malarial inoculations, have shown that eighteen grains of quinine 
daily for five days before and seven days after mosquito bites by infected 
Anopheles failed to avert an attack, but that when the drug was continued 
for ten days after the insect bite, the disease did not develop. These experi- 
ments, they believed, demonstrated that quinine had little or no effect on the 
infecting sporozoites, but only acted on the developed trophozoites in the red 
corpuscles of the blood. From their work it seems evident that quinine, taken 
before and for a few days only after being bitten by mosquitoes infected with 
malarial parasites, may fail to avert infection, but that if continued for ten 
days or longer after the insect bite, it prevents malarial attacks. Prolonged 
daily prophylactic quinine acts either by curing an attack of malaria at its 
onset by killing off the parasites after infection of the corpuscles has taken 
place, or by so reducing the degree of infection both in sporozoites and in tropho- 
zoites that an infection that otherwise would be severe becomes mild or compara- 
tively harmless. 
Craig *® has recently reviewed the subject of the action of quinine on the 
malarial plasmodia. He concurs in the idea that, either directly or indirectly, 
quinine does destroy the malarial parasite in the blood of man. However, 
although he also believes that malarial infection cannot always be prevented, 
even though as much as one gram of quinine is taken daily for prophylaxis, 
he is emphatic in saying that this amount will prevent the appearance of symp- 
toms so long as it is taken, and that therapeutic doses will cure the infection 
even before:the development of symptoms. A most important piece of research 
in respect to quinine prophylaxis in the field has recently been carried out by 
MeNabb and Stewart.? These medical officers made their observations on 
three companies of United States Army Engineers employed in mapping Panama. 
Quinine prophylaxis was compulsory; under strict supervision one gram of 
quinine was given each soldier daily in tablets or capsules before the evening 
meal. The men worked and were camped in intensely malarial places. The 
1 Yorke and Macfie: Trans. Royal Soc. Med. and Hyg. (1924), XVIII, 13. 
2 Craig: Arch. Path. (1928), VI, 704. 
3 McNabb and Stewart: Amer. Jour. Trop. Med. (1927), VII, 357. 
