384 TYPHOID FEVER 



to the action of toxins ; here it is important to note that the 

 poisons formed by this group of organisms are relatively heat- 

 resisting, so that boiling for a time does not destroy the toxicity. 



The Psittacosis Bacillus. When parrots are imported from the 

 tropics in large numbers, many die of a septicaemio condition in which an 

 enteritis, it may be hsemorrhagic, is a marked feature. There is intense 

 congestion of all the organs and peritoneal ecchymoses. From the 

 spleen, bone marrow, and blood there has been isolated a bacillus having 

 the group characters, except that here also an effect on lactose has 

 been described. The parrot is most susceptible to its action, but it 

 also causes a fatal h?emorrhagic septicaemia in guinea-pigs, rabbits, mice, 

 pigeons, and fowls, the bacilli after death being chiefly in the solid 

 organs. From affected parrots the disease appears to be readily 

 communicable to man, chiefly, it is probable, from the feathers being 

 soiled by infective excrement. Several small epidemics have been 

 recognised and investigated in Paris. After about ten days' incubation, 

 headache, fever, and anorexia occur, followed by great restlessness, 

 delirium, vomiting, often diarrhoea, and albuminuria. Frequently 

 broncho-pneumonia supervenes, and a fatal result has followed in about 

 a third of the cases observed. The organism has been isolated from the 

 blood of the heart. The psittacosis bacillus is evidently one of the 

 typhoid group, a fact which is further borne out by the observation tlmt 

 it may be clumped by a typhoid serum. The clumping is, however, said 

 often to be incomplete, as the bacilli between the clumps may retain 

 their motility. It differs from the typhoid bacillus in its growth on 

 potatoes and in its pathogenicity. 



Danysz's Bacillus and Rat Viruses. Danysz isolated from an 

 epizootic in field mice an organism of this group, which he introduced 

 for the purpose of killing rats by originating in them through feeding a 

 similar epizootic, and several viruses of this kind are in commercial use 

 for this purpose. These have been investigated by Bainbridge, who, 

 however, finds that they owe any efficiency they possess to two organ- 

 isms, the bacillus Aertryck and the bacillus enteriditis of Caertner. The 

 efficacy of such agents varies, and the mortality in artificially originated 

 epizootics is from 20 to 50 per cent. Sometimes, apparently under 

 natural conditions, rats develop an immunity to those viruses, and it is 

 doubtful whether they are entirely innocuous to other animals which 

 may partake of the food containing them. 



BACILLARY DYSENTERY. 



Dysentery has for long been recognised as including a number 

 of different pathological conditions, and within more recent times 

 amoebic and non-amoebic forms have been distinguished. Of the 

 latter, bacteria have been believed to be the causal agents, and an 

 organism described by Shiga in 1898 has almost certainly been 

 established as the cause of a large proportion of cases. Shiga's 

 observations were made in Japan, and confirmatory results have 

 been obtained by Kruse in Germany, by Flexner and by Strong 

 and Harvie in the Philippine Islands, and more recently by Vedder 



