394 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ IV, IV.

cultural changes represent the true developmental cycle, then there appears to be
some relationship between crithidia tabani and the cultural forms of T. theileri.

Noller [1916] concluded that Crithidia subulata Ledger, 1904, from the gut of
Tabanus glaucopis is the developmental form of T. theileri. Wenyon [1926] sug-
gests that if Crithidia subulata is the insect phase of T. theileri, the other similar
flagellates of tabanidae and their allies may also be the developmental form of the
trypanosomes. Noller [1925] appears to have established this identity in the case
of crithidia from Haematopota pluvialis. He injected clean calves with cultures of
flagellates of that fly and recovered T. theileri in the blood cultures of those calves.
We have said above that we injected crithidia found in tabanus flies caught in
Kaveripakam, into calves with negative results. In nature, if cattle are to get
infected with T. theileri, it should be with developmental forms directly from an
insect vector. Since the method employed by us is direct from the fly to the calf
through the needle, as done by Noller, it is not understood why our experiments
failed to produce T. theileri in the calves. One calf was drenched with the
crithidial forms of T. theileri in culture. Even this calf failed to show the trypano-
somes in blood cultures made from it.

During the past three years it has been possible to culture the blood of over
200 virus producing calves, and the blood of only one calf showed the cultural
forms of T. theileri. In one calf recently, T. theileri was seen in its blood in fairly
large numbers a few hours before it died of rinderpest.

In this Laboratory during the year 1928-29, T. theileri has been recorded in the
blood of a few calves used for rinderpest virus production, in a cow in a dairy at
Coonoor and a calf at Madanapalli [Rao and Ayyar,[1931]. The blood culture
experiments show that an extremely small percentage of animals show T. theileri
and it may be said that these parasites are not commonly found in bovines,
though it is possible that the regional distribution is wide. Our experimental work
also shows that it is doubtful if C. tabani have any relation to T. theileri.

                                             SUMMARY.

Experimental evidence shows that the smaller trypanosomes found in cattle.
dogs and ponies in S. India are identical with T. evansi.

The small trypanosomes found in cattle are pathogenic to horses when inocu-
lated to them.

There appears to be little experimental evidence to prove that cattle and
buffaloes form reservoir hosts of T. evansi.