21 
blood ; anemia rapidly becomes marked and the number of leucocytes 
and parasites is very great. Occasionally many free vermicules are 
observed shortly before death. 
In rats vdth heav}^ infection there is marked apathy, little food is 
taken, and the animal sleeps constantly, mth the head tucked under 
the thorax. 
The anemia is most striking. The ears and skin, as well as the 
mucous membranes, become pearly white. When blood is drawm 
from the tail it is thin and watery, and it is very difficult to make a 
smooth smear. When death occurs after a long period there is great 
emaciation. The temperature ma}^ rise as liigh as 38.6° C. 
Shortly before death there is often diarrhea, with an occasional ad- * 
mixture of blood, and the temperature is subnormal. In one animal 
hemoglobinuria was observed. 
Lethality . — Of the 17 rats originally found infected, 4 died. How- 
ever, 4 which showed severe infection were cliloroformed to provide 
material for inoculation and fresh tissue for sectioning. Of 16 rats 
infected experimentally, 8 died — a lethality of 50 per cent. Young 
rats appear to be most susceptible and the majority of the fatal infec- 
tions were in animals not fully grovm. In half-grown rats the disease 
is almost invariably fatal in a few days after the onset of symptoms. 
PATHOLOGICAL ANATOMY. 
The gross lesions are most marked in animals wliich succumb to 
infection. In chronic infections the animals are much emaciated. 
The muscles and mucous membranes are extremely pale. The 
heart’s blood is tliin and watery. The lungs frequently show minute 
hemorrhages upon the surface. The spleen is greatly enlarged and 
dark in color; it may be five or six times the normal size, and fre- 
quently reaches from the diaphragm diagonally across to the right 
side of the brim of the pelvis. The small intestine occasionally con- 
tains thin fluid blood. The mesenteric glands are enlarged, some- 
times hemorrhagic. The liver is distinctly enlarged, dull yellow in 
color, sometimes mottled, and the thin borders are rounded. Smears 
and frozen sections show extensive fatty changes. The kidneys show 
moderate parenchymatous degeneration. The urine rarely contains 
hemoglobin; more often bile pigment. The bone marrow is red. 
THE ARTHROPODA AS AGENTS IN THE TRANSMISSION OF DISEASE. 
The sexual cycle of Hepatozoon perniciosum takes place in a parasitic 
mite (an acarien), XeZaps echidninus Berlese. Mr. Nathan Banks, of 
the United States Department of Agriculture, has kindly made the 
determination. From a careful search of the literature it appears 
that this is the first recorded instance in which a member of the 
