1908-9.] The Pathogenesis of Micrococcus melitensis. 549 
glutinous, and not present in very large amount ; while numerous yellow 
flakes consisting of polymorphonuclear leucocytes and micrococci are 
scattered all through the peritoneal cavity. In the case of the male animal 
the epididymis and vasa at first sight appear like clots of blood, from the 
excessive engorgement of their vessels. The testis itself is swollen and red, 
and on incising the organ the tunica vaginalis is found to be adherent to 
the body of the testis, bound down by sticky gelatinous pus, the interstices 
between the adhesions being occupied by a thin sero-pus containing flakes 
of fibrin. In the inspissated pus or in the sero-purulent fluid M. melitensis 
is particularly abundant. The spleen is large, generally of a dark red colour ; 
the Malpighian corpuscles are very prominent ; the organ itself is firm and 
tense owing to the pressure within the capsule, but on incising the organ 
the spleen pulp is frequently almost fluid. Cultures from all the organs 
yield copious growth of M. melitensis, the heart blood is full of cocci, and 
occasionally the urine contains a few, which have probably gained access 
through the peritoneum covering the walls of the ureter and the bladder. 
The temperature, weight, and agglutination curves of such an infection 
are shown in chart 5. 
2. Chronic . — The course of a chronic intraperitoneal infection does not 
differ in any material respect from that of the chronic intravenous infection 
(see chart 6) beyond the length of time that usually elapses between inocula- 
tion and death. In the former case this period may extend to six or seven 
months ; in one of my cases thirteen months intervened. Post-mortem, no 
macroscopical lesions are present, the peritoneal cavity and the abdominal 
viscera are normal in appearance, and as a rule cultures of M. melitensis 
can only be obtained from the centrifugalised deposit of the bladder con- 
tents, or from the kidney tissue if large pieces of that organ are planted in 
broth. Occasionally all cultivations remain sterile, and the presence of 
specific agglutinins in the blood and changes in the histological structure 
of the blood and bone marrow form the only evidence of infection. 
D. Subcutaneous Inoculation. — 1. Acute . — No amount of experimental 
exaltation of the virulence of M. melitensis has yet enabled me to produce 
an acute infection of the rodent as the result of subcutaneous inoculation — 
the infection, so far as relates to the fatal termination, is always and 
extremely chronic. Again, unless the organism has been previously exalted 
in virulence by means of passages through animals of the same species, 
pus formation is the exception rather than the rule, and it is often difficult 
to obtain any evidence of successful infection, other than the presence of 
specific agglutinins in the blood-serum, if the process is allowed to pursue 
its natural course. 
