36 
with. The sporozoites in such cysts do not appear to differ from 
those in the other cysts mentioned. 
When ruptured by pressure, the cysts split in the direction of great- 
est length, the edges curling up. In sections of mites (pis. ix, x, 
xix) showing large oocysts containing sporoblasts or sporocysts the 
outlines of the large cysts are somewhat irregular and not clearly out- 
lined. Also, the varying effect of the pressure of surrounding organs 
and the shrinkage and distortion in fixation and embedding cause the 
large cysts to assume a variety of forms other than spherical. 
The invasion of the salivary glands by the cysts is particularly 
interesting. In some specimens the gland on one or both sides has in 
part or entirely disappeared and been replaced by the parasites. 
The sporozoites have never been found free, however, in such sec- 
tions nor in fresh preparations, but always inclosed in the sporocysts. 
The possibility of the transmission of the parasite through the salivary 
glands and their appendages will be considered later. 
In the study of the various stages which have just been described 
sections from a great number of mites and fresh preparations from 
hundreds of both normal and infected mites have been utilized. The 
observations were repeated and verified many times. 
The presence of the parasites in moderate numbers does not appear 
to be injurious to the mites. Mites have frequentty been observed, 
with fresh blood in the stomach and ripe sporocysts in the bod}^ tis- 
sues. However, those found dead have often been very heavily 
infected. 
EXPERIMENTAL INFECTION IN WHITE RATS. 
Although Christophers has described what he regarded as the sexual 
cycle of Leucocytozoon cams in a tick, he states in a recent volume ® 
that ‘Hhe sexual cycle can not }^et be said to be definitely known.’’ 
Certainly the experimental transmission of hsemogregarines by 
arthropoda or b}^ direct inoculation has not, so far as the literature 
records, been successful^ accomplished. 
In the present work it was recognized that the conditions for experi- 
mental attempts at transmission of H. perniciosum were extremely 
favorable, the principal host being, so to speak, a domesticated animal, 
and therefore readih^ handled. The intermediate host — the mite — 
could easil}^ be obtained in large numbers and its action was suscepti- 
ble of complete control. In fact, all the conditions of natural infec- 
tion could readily be reproduced artificially. 
As alread}^ stated, a large number of mites (several hundred) 
were infected by being placed upon heavily infected rats for forty- 
eight hours or longer and then transferred to healthy rats for ten to 
a Stephens, J. W. W., & Christophers, S. R.: The practical study o£ malaria. 3d ed. 
London, 1908, pp. 1AH4. 
