As a rule, however, the entire large intestine is grayish red, looking like lustreless red velvet. Later on we may have irregular islands of grayish membrane formation surrounded by the red swollen congested gut. The solitary glands are usually swollen and may soften and ulcerate, having the submucosa as a base. Ulceration in bacillary dysentery is superficial rather than deep as with amoebic dysentery. The ulcers of bacillary dysentery involve the free folds of the intestine and extend transversely while amoebic ulcers run longitudinally. The intervening mucosa is unaffected in amoebic ulcerations while in bacillary ones it is inflamed. Microscopically we note marked congestion of the blood vessels of the mucosa and submucosa with dilated lymph spaces full of polymorphonuclear cells. In the mucosa we find an outpouring of pus cells which are entangled, along with the glandular structures of the mucosa, in a fibrinous exudate which causes necrosis of the mucosa (coagulation necrosis). In chronic bacillary dysentery, according to Rogers, the lesions are limited to the lower portion of the large gut and rarely extend above the descending colon. In this region one finds serpiginous ulcerations separated by islands of mucosa. Willmore and Savage have noted autopsy findings of what was practically a large granulating surface over the whole large intestine, in cases which had apparently recovered, with the exception of a prolonged convalescence. SYMPTOMATOLOGY Bacillary dysentery usually runs an acute course, rarely relapsing and but occasionally going on to a chronic condition. The period of incubation is usually from two to seven days although accidental infection with bacilli in the laboratory has given an incubation period approximating twenty-four hours. Periods of incubation longer than a week can probably be explained as for cholera, such cases being in those who are healthy carriers, but by reason of some gastro-intestinal upset the quiescent bacilli take on pathogenic activity. In temperate climates and in particular when the infecting organism is a Flexner type the case may appear as a watery diarrhoea associated with colicky pains and anorexia. The stools soon become more scanty in amount, frequent in number and associated with straining. This is followed by mucous stools more or less tinged with blood. The temperature is normal or but slightly elevated and the patient does not seem ill.