Gr. H. F. Nuttall and S. Hadwen 
231 
of the two Control Dogs (A) died of piroplasmosis on the 10th day after 
inoculation. Control Dog B remained well up to the 23rd day after 
inoculation, thus in a measure vitiating the experiment. We neverthe¬ 
less consider that the result confirms the experiment on Dog 13, reported 
in our previous paper, and cited on p. 229, for the following reasons. It 
is a relatively rare occurrence for an inoculation to fail to produce 
infection. In our previous paper we recorded 25 consecutive inoculations, 
in which only one (Dog 12, p. 186) failed to give a positive result by the 
11th day, when the dog was reinoculated. The only dog which did not 
show parasites was Dog 13. Again, all of the five dogs used in the 
remaining experiments described in this paper died from piroplasmosis as 
the result of inoculation. We conclude therefore that Trypanblau injected 
a day before or a day after inoculation prevents the development of the 
disease by destroying the parasites. 
It is not quite certain upon what the negative result of the inocula¬ 
tion depended in the case of Dog B. In the few cases observed by one 
of us (N.), in the course of the last five years, where inoculations have 
failed to infect, the negative result could not be attributed to the 
existence of any immunity on the part of the dog. Upon reinoculation 
such dogs have invariably acquired the disease. We are inclined to 
believe that the negative result is attributable to mechanical causes, 
the injected blood remaining confined to the subcutaneous or cellular 
tissue at the seat of inoculation. Under such conditions the parasites 
cannot gain access to the blood corpuscles of the host, because they re¬ 
main enclosed within an impervious limiting membrane, at any rate for 
a sufficient length of time to cause the parasites to perish from lack of 
fresh corpuscles, into which they must soon penetrate if they are to 
survive. The matter is not without interest and deserves investigation. 
To render infection certain, on the assumption that our explanation 
holds good, all that appears necessary is to massage the seat of the 
blood injection so as to prevent the blood from remaining confined as it 
were in a bag. 
Experiments with Trypanblau given by the Mouth. 
Owing to the objection on the part of owners of cattle against modes 
of treatment which necessitate the use of a syringe whereby remedies 
are injected either subcutaneously or intravenously, it appeared to us 
expedient to try if trypanblau exerted any effect upon the parasites 
when the dye was given by the mouth. 
