558 Proceedings of the Royal Society of Edinburgh. [Sess. 
this family were the subjects of M. melitensis infection naturally acquired. 
Thus the horse and mule, by reason of the presence of often large amounts 
of specific agglutinin in the blood serum, were considered to be subject to 
natural infection, though the specific organism was never recovered from the 
tissues. The cow, goat, and sheep yielded stronger evidence, as the micro- 
organism was successfully isolated from the milk of some of the females in 
each species. The number of cows upon the island was too few to give any 
reliable information as to the percentage incidence of M. melitensis septicsemia; 
but in the case of the goat, which in Malta is the commonest quadruped, 
and numbers some 20,000 head, this point was studied by means of a careful 
examination of a large number of individuals, and from the results obtained 
it is estimated that nearly 30 per cent, are or have been the subject of 
M. melitensis septicaemia naturally acquired, while fully 10 per cent, yield 
absolute proof of present, though chronic, infection by the presence of the 
micrococcus in their milk. Having had no personal experience of the 
infection of mules, cows, or sheep by laboratory methods, I shall confine my 
remarks to the experimental inoculation of the horse and of the goat. 
Horse . — The horse I have infected by means of intravenous injections 
in the course of some immunising experiments whilst attempting to prepare 
an anti-serum. The clinical phenomena observed after inoculation of this 
animal — a chestnut mare — were remarkably few. The temperature rose 
within a few hours, but rarely more than T5° C. to 2° C., and the mare was 
u off her feed ” for perhaps twenty-four to thirty-six hours. The tempera- 
ture rapidly returned to normal, the coat remained smooth and glossy, and 
the animal appeared to be perfectly normal. Examination of the blood, 
however, showed the presence of specific agglutinins, and the cocci were 
present in the general circulation for between three and four weeks after 
each injection (chart 11). 
The goat , so far as my observation carries me, is never the subject of an 
acute infection, though it is true I have never employed the intracranial 
method of inoculation of this animal. The animal is susceptible to infection 
as the result of intravenous (see chart 12), intraperitoneal, subcutaneous, and 
cutaneous injection of M. melitensis, and also by feeding methods. By 
whatever method the infective material is introduced into the tissues, the 
clinical phenomena are similar. The animal rarely appears to be adversely 
affected. Its appetite is as vigorous as ever, and beyond a few days’ pyrexia, 
during which the coat may or may not lose a little of its sheen, nothing 
can be detected by the ordinary clinical methods of observation. 
Examination of the blood from time to time shows the presence in the 
serum of specific agglutinins, first demonstrable in from seven to twenty-one 
