546 Proceedings of the Royal Society of Edinburgh. [Sess. 
becomes dull and apathetic ; sits huddled up in one corner of the cage, and 
refuses food. The temperature rises rapidly to 41°, 42°, or 43° C. ; the 
body weight falls rapidly, and the animal finally becomes dyspnoeic, death 
supervening in from two to four days. Post-mortem, beyond engorgement 
of the viscera and dilatation of small blood-vessels, nothing abnormal can 
be detected. The agglutination titre of the serum is, as a rule, low — not 
more than 1 : 50 — rarely it may be as high as 1 : 200 or 1 : 400. Cultiva- 
tions from all the organs and from the heart blood give rise to luxuriant 
growth of M. melitensis. Chart 3 is typical of this infection. 
2. Chronic . — The converse of the conditions of inoculation enumerated 
above give rise to the chronic form of infection. Here the clinical pheno- 
mena detailed under the acute infection are less marked, although the 
same sequence of events is at first noted. The animal refuses food, is 
obviously uncomfortable ; the temperature rises in the same way, but rarely 
above 40° C. ; the weight falls, but as a rule not more than about 10 per 
cent, of the body weight is lost. After three or four days the general 
condition improves ; the animal takes its food eagerly, even ravenously, 
and commences to put on weight again, but usually never regains its 
original weight. After a week or two it again loses weight. Suddenly, at 
the end of seventeen to twenty days, or even after a lapse of a month or 
two, the animal dies. 
Post-mortem, no abnormal conditions can be detected, and cultivations 
from the heart blood and various organs, including the glands, remain 
sterile. Cultures from the centrifugalised deposit of the urine may give 
rise to a sparse growth of M. melitensis. Occasionally, too, if large pieces of 
kidney tissue are planted in flask broth cultures, a scanty growth of the 
micrococcus can be obtained. Such a case is shown in chart 4. 
C. Intraperitoneal Inoculation . — Intraperitoneal inoculations of recently 
isolated strains of M. melitensis, as a rule, only provoke an infection 
characterised by extreme chronicity, even when large doses are injected 
into young animals. Intravenous passages certainly increase the virulence 
of M. melitensis for rodents by all methods of inoculation to a very marked 
degree, but the only really satisfactory and certain method of so increasing 
the virulence of this organism that acute intraperitoneal and subcutaneous 
infections can readily be produced, consists in a number of preliminary 
passages through brain tissue. This selective affinity of M. melitensis for 
the nerve cell undoubtedly has some bearing upon nerve symptoms so 
frequently observed in M. melitensis septicaemia as it occurs naturally in 
man, and is a subject that affords ample scope for future experimental 
investigation. 
