41 
severe infection with II. pernieiosum. At the end of six weeks the 
remaining rats were all infected with the blood parasite, but in a 
mild degree. At the end of eight weeks the animals still show the 
parasite. The age of the rats at the beginning of the experiment is 
assumed to be about four months. 
FEEDING EXPERIMENTS. 
Ten rats were selected and placed in isolated glass jars with gauze 
tops. Each cage, as well as each rat, was sprinkled with “insect 
powder.’’ All the rats were carefully examined and found free of 
vermin except a few lice. These disappeared within a few days after 
the “insect powder’* was used. 
Blood smears from each rat were examined on two successive days. 
The blood was normal and showed no parasites. Before the feedings 
with infected material all food was withdrawn for forty-eight hours. 
Mites containing ripe sporozoites were crushed singly or in small 
numbers at a time upon double-width glass shdes. Immediately 
after crushing, examination with the low power of the microscope 
was frequently resorted to, in order to be certain of the abundance 
of ripe sporocysts. Pieces of moistened wliite bread were used to 
absorb the expressed juices of the crushed mites. After a thin piece 
of bread about 2 cm. square had received from 15 to 20 or more 
crushed mites and their juices it was gently compressed into a firm 
round mass and immediately fed to a rat. In this manner eight of 
the ten rats were fed. The other two were kept as controls. The 
eight rats were fed as described only once ; afterwards ordinary food 
(bread and oats), was given. 
Twenty-four hours after the infected bread was given, and every 
day thereafter, stained blood smears, and on occasion, fresh prepara- 
tions, were examined. In the first twenty-four hour preparations, 
five rats showed a moderate number of actively moving free vermi- 
cules in the blood: they were also observed in stained smears and 
differed in no way from those previously described. The leucocytes 
were but little if at all increased in number : no encysted or other 
variety of parasites were observed. TThen next examined (third day) 
no parasites were observed in any of the smears examined. The later 
findings are given below: 
Bat Xo. 1 . — A small number of encysted parasites observed on 
the eighth day; on twelfth day moderate anemia; parasites greatly 
increased, also leucocytes: death on fourteenth day. 
Post-moHem . — Enlarged spleen, fatty fiver. 
Bat Xo. 2 . — Moderate numbers of encysted and a few free para- 
sites observed on twelfth day; gradual increase in number up to 
fortieth day; animal shows moderate anemia and seems sick: en- 
cysted parasites numerous. 
