166 Major R. Ross and Dr. D. Thomson. [ Oct. 12, 
6. Lhe Degree of Fever Associated with Various Numbers of Parasites.— 
We know of no extensive and exact studies on this point, and ours are not 
yet complete. On 47 occasions the number of parasites was carefully 
compared with the maximum degree of temperature reached during the 
febrile paroxysm caused by them, and the following results were obtained :— 
: 
P. vivax (12 occasions). 
No. of parasites ............... | 1500 1400 580 | 440 430 260 256 
Maximum temp., deg. H.F. 84 101 O97 a 102 76 76 54 
ING FOLMPATASILES 6.4.2... sons40 | 232 150 133 100 83 
Maximum temp., deg. H.F. | A6 44, 34 34: 20 
¢ (rigor) 
(Coefficient of correlation), 7 = 0 68561 +0 °10318. 
P. falciparum (35 occasions). 
No. of parasites................ 303,000 58,000 55,000 54,000 50,000 45,000 
Maximum temp., deg. H.F. 108 82 88 100 98 76 
Nosoteparasites 0:0. 60 ae. 36,000 34,000 31,000 26,000 26,000 25,000 
Maximum temp., deg. H.F. 60 86 76 94. 101 80 
No. of parasites ............... 16,000 | 15,000 | 15,000 | 15,000 | 9,700 | 9,000 
Maximum temp., deg. H.F. 52 54 54 70 56 70 
No:tof parasites (4020.2... 7,500 7,400 6,700 6,500 6,000 5,800 
Maximum temp., deg. H.F. 90 40 86 83 52 70 
No. of parasites (3... ..2..00.: ~ 5,200 4,000 4,000 3,600 3,000 2,600 
Maximum temp., deg. H.F. 76 70 40 80 38 64 
No. of parasites ....00......... 2,500 | 2,000 | 1,860 | 1,000 200 
Maximum temp., deg. H.F. 50 46 38 15 50 
(Coefficient of correlation), 7 = 0 6033140 07251. 
These figures, together with the numerous ones given in the table of cases, 
show a very marked correlation, but there are, of course, many minor 
deviations. In numbers of the specimens there were certainly two sets of 
parasites of different ages, which were often counted together, though only 
one set could have been concerned with the fever. It is probable also, 
though by no means certain, that the resistance to the toxin of the Plasmodia 
varies, not only in different persons, but in the same person at different 
stages in the course of his infection and under different physiological 
conditions. Our new methods will, we hope, enable us shortly to undertake 
_very detailed studies on these points. 
7. The Pyrogenice Limit.—it is quite evident that if the parasites fall below 
a certain limit, they are no longer numerous enough to cause fever. Thus 
with P. vivax, an average of 125 parasites of all ages and forms counted 
during 68 days in 8 cases, and with P. falciparum an average of 460 asexual 
forms counted during 83 days in 19 cases, failed to produce fever. The actual 
limit above which they become pyrogenic probably varies in different cases. 
With P. vivax, as many as 1500, 852, and 540 were found in Cases 2, 6, and 7 
