394 THE HUMAN SPECIES 



carrier of the infection ; as this is found on rats and apes it is 

 possible that these animals also are infected, as well as man. 

 This would form an important distinction between the African 

 and European recurrent fevers. 



All the diseases hitherto described have been caused by 

 bacilli. Pneumonia illustrates the transition from the bacillary 

 to the coccal form of organism, as both the bacillus of Fried - 

 laender and the coccus of Fraenkel play a part in its causation 

 (Plate V., figs. 6 and 7). Inflammation of the lungs caused 

 entirely by the bacillus only occurs in man. Artificial infections 

 have a marked effect only in mice and guinea-pigs ; rabbits are 

 immune. The pneumococcus, on the other hand, gives rise to 

 spontaneous attacks not only in man but also very frequently 

 in animals ; in all cases of artificial infection the appearances in 

 the lungs and other organs are similar to those found in man. 



We will now pass on to the description of the remaining 

 diseases caused by cocci, of which we may remark that their 

 influences both locally on the tissues and generally on life and 

 health is the same in man and in the other animals. The 

 danger to life is less with the staphylococci which produce pus ; 

 both in man and animals, and in the latter also under experi- 

 mental conditions, pus formation, abscesses and boils are produced. 

 Streptococci are more dangerous, not only on account of their 

 tendency to increase in the body of the patient, but also on ac- 

 count of their power to set up erysipelatous inflammations, and 

 so to produce general blood-poisoning, or sepsis. As regards 

 this there is no difference between man and other animals. 



Malta fever is a disease peculiar to man, and commonly 

 observed among the inhabitants of Malta. The cause of the 

 disease had been vainly sought for some time, when Bruce in 

 1896 discovered and described the coccus Melitensis (Plate V., 

 fig. 8). Recent investigations by the English Commission has 

 shown that the goat acts as-a carrier of the organism, and through 

 its milk transmits the disease to man. Inoculation experiments 

 with cultures of this coccus produce in monkeys (and in these 

 animals only) a fatal disease showing the same symptoms as 

 that in man. 



Acute articular rheumatism and meningitis are diseases 

 caused by cocci in combination with some other agent. In 



