776 PASTEUBELLA 



lesion and the nearest glands ; they are usually irregular in size and shape, exhibit bipolar 

 staining, and may show involution forms. They are often present in the spleen and in 

 the blood. If the animal lives for a week, small, irregular, necrotic foci may be observed 

 in the spleen and liver. 



The German Plague Commission (Report 1899) had apparently no difficulty in infecting 

 rats by the mouth, but other workers have not been so successful. They fed the animals 

 with a drop of plague culture or with the cadaver of a rat that had died of plague. Death 

 followed uniformly in 2 to 3 days. Post mortem, three types of lesion were found, (a) Most 

 commonly enlargement and congestion of the submaxillary and suprahyoid glands, with 

 the general picture of septicaemia. (6) Less often primary infection of the stomach and 

 intestine, numerous punctiform haemorrhages round the pylorus, swelling and hsemorrhagic 

 infiltration of the lymph follicles and mesenteric glands, which were often quite large, and 

 contained innumerable plague bacilli, (c) Quite frequently an aspiration pneumonia ; 

 the lungs showed inflammatory foci of varying size, containing large numbers of plague 

 bacilli ; the spleen was enlarged, and the liver hjrpersemic. 



The English Plague Commission had less success with feeding. Of the wild rats of 

 Bombay only 38 per cent, were found to be susceptible when fed on the carcasses of dead 

 plague rats. In the Punjab the proportion was nearly 70 per cent. The lesions found in 

 rats infected by feeding were of a similar type to those in rats infected naturally. Two 

 striking differences, however, were present, (a) In naturally infected plague rats the bubo 

 is in the neck ; a mesenteric bubo was not encountered in 5,000 examinations : in the case 

 of fed rats the bubo is generally in the mesentery. (6) In naturally infected rats the stomach 

 and intestines show no marked pathological changes : in rats infected by feeding well- 

 marked lesions are found in the intestines — haemorrhages in the stomach waU 3 per cent., 

 congestion of intestines 27 per cent., enlargement of Peyer's patches 31 per cent. 



The nasal mucosa and conjunctiva are favourable spots for inoculation in rats (Report 

 1899). A trace of infective material smeared over the conjunctiva proves fatal in 3 to 

 4 days. Post mortem, there is swelling of the cervical lymph glands, enlargement of the 

 spleen, and frequently numerous haemorrhages in the stomach and jejunum. The appear- 

 ances are in fact similar to those of an animal dying after oral infection. Contamination 

 of the nasal mucosa is frequently followed by an inhalation pneumonia. 



The English Plague Commission (Report 1912, p. 287) were able to reproduce the 

 lesions of chronic or — as they prefer to call it — of resolving plague in rats by inoculating 

 large numbers of animals with small doses, and retaining the survivors for 3 weeks after 

 inoculation. The chief lesions foimd were chronic buboes, necrotic areas in the spleen, and 

 chronic abscesses in the spleen or more rarely the liver. 



Mice. — The mouse reacts to inoculation in much the same way as the rat. After 

 subcutaneous inoculation the septicaemia is very marked ; the blood and internal organs 

 swarm with bacilli. Infection can be accomplished by feeding, if a sufficiently large dose 

 of a virulent culture is used. 



GuiNEA-PiGS.^Guinea-pigs are highly susceptible to plague, dying in 2 to 5 days after 

 subcutaneous injection of a pure culture. Post mortem, there is a necrotic focus at the site 

 of injection surrounded by intense congestion and ojdema ; the regional lymph glands are 

 swollen and embedded in a bloody oedema ; their interior is soft and necrotic. There is 

 enlargement and congestion of the spleen, which is often studded with miliary, soft, grey 

 nodules up to 1 mm. in diameter, sometimes projecting above its surface, and containing 

 large numbers of bacilli. The suprarenals may be congested (Yersin 1894). The liver 

 mav be peppered with tiny necrotic foci, and occasional small necrotic nodules are visible 

 in the lungs. Sometimes there is a pleural effusion. Guinea-pigs can be infected by 

 the cutaneous route. If the plague material is rubbed on the shaven skin of the abdomen, 

 an inflammatory reaction appears in the neighbourhood, marked by a sUght reddening 

 and the formation of umbilicated pustules in which plague bacilli are present (Dieudonne 

 and Otto 1912). After a few days the regional glands swell and death occurs in 4 to 5 days. 

 The post-mortem signs are similar to those after subcutaneous inoculation. 



