410 CHOLERA. 



tion, as they have no higher powers of resistance than the 

 spirilla themselves, and cultures containing enormous numbers 

 of such bodies may be found to be quite dead. Along with such 

 appearances in old cultures there is found great change in the 

 size and shape of the organisms (Fig. 140). Some are irregu- 

 larly twisted filaments, sometimes globose, sometimes clubbed 

 at their extremities, and also showing irregular swellings along 

 their course. Others are short and thick, and may have the 

 appearance of large cocci, often staining faintly. All these 

 changes in appearance are to be classed together as involution 

 forms. 



Staining. Cholera spirilla stain readily with the usual basic 

 aniline stains, though Loffler's methylene-blue or weak carbol- 

 fuchsin is specially suitable. They lose the stain in Gram's 

 method. 



Distribution within the Body. The chief fact in this connec- 

 tion is that the spirilla are confined to the intestine, and are not 

 present in the blood or internal organs. This was determined 

 by Koch in his earlier work, and his statement has been amply 

 confirmed. In cases in which there is the characteristic " rice- 

 water " fluid in the intestines, they occur in enormous numbers 

 almost in pure culture. The lower half of the small intestine 

 is the part most affected. Its surface epithelium becomes shed 

 in great part, and the flakes floating in the fluid consist chiefly 

 of masses of epithelial cells and mucus, amongst which are 

 numerous spirilla. The spirilla also penetrate the follicles of 

 Lieberktihn, and may be seen lying between the basement 

 membrane and the epithelial lining, which becomes loosened by 

 their action. They are, however, rarely found in the connective 

 tissue beneath, and never penetrate deeply. Along with these 

 changes there is congestion of the mucosa, especially around the 

 Peyer's patches and solitary glands, which are somewhat swollen 

 and prominent. In some very acute cases the mucosa may show 

 general acute congestion, with a rosy pink colour, but very little 

 desquamation of epithelium, the intestinal contents being a com- 

 paratively clear fluid containing the spirilla in large numbers. 

 In other cases of a more chronic type, the intestine may show more 

 extensive necrosis of the mucosa and a considerable amount of 

 haemorrhage into its substance, along with formation of false 

 membrane at places. The intestinal contents in such cases are 



