240 THE INFECTIOUS DISEASES. 



Characters of the Cholera Spirillum. 



The cholera spirillum, which was discovered by Koch in 1883, is a curved rod with 

 rounded ends from, 0.8 to 2.0 // long, asporogenous, aerobic, and motile. When growing 

 under suitable conditions these rods are apt to cling together by their ends, forming S- 

 shaped structures or spirils, often of considerable length (Fig. 116.) The organism stains 

 readily and grows abundantly on the ordinary culture media. The life period is short 

 and various degenerative " involution " forms are apt to be present in old cultures. It 

 grows best at about blood heat; growth ceases at about 16 C., but may survive a re- 

 duction of the temperature to 10 C. It is quickly killed 

 by drying or by the temperature of boiling water. Acids 

 are inimical to its growth. It may retain its vitality for 

 a considerable time in water. On moist surfaces, such as 

 damp linen, earth, vegetables, or in milk, it may rapidly 

 proliferate. 



The results of animal experiments with the cholera 

 germ are not in themselves decisive in determining its 



FIG. 116.~SiMRii.LUM CHOLERA re i at i onsh jp to this disease, since animals do not react in 

 its presence as man does. However, the constant occur- 

 rence of this organism in Asiatic cholera, its absence from 

 the body under other conditions, and the accidental labo- 

 ratory infections which have several times occurred in men handling pure cultures of 

 the germ, leave no doubt as to its significance as the excitant of this disease. 



The infectious organism is usually conveyed from one person to another by the 

 pollution of food or drink with the discharges which contain the virulent germs. 



It is often of the highest importance to determine, at the earliest possible moment, 

 whether or not a suspected case be one of Asiatic cholera or some other form of acute 

 intestinal disorder, so that in the former case the proper measures may be instituted to 

 prevent the spread of the disease. The characters which are developed in cultures of 

 the cholera bacillus enable an expert bacteriologist to distinguish this organism from 

 all other known forms. But the scope of this work does not permit a detailed descrip- 

 tion of the cultural peculiarities of the germ. Nor should the responsibility of such de- 

 terminations be assumed without adequate preliminary laboratory experience. By 

 taking together the morphological and biological characters, it is possible, usually on the 

 second or third day, to determine whether the intestinal contents of a suspected case do 

 or do not contain the bacillus of Asiatic cholera. 1 



Preventive Inoculation, Antitoxic Cholera Serum and its Lysogenic Action. 



A large amount of work has been done, looking toward artificial immunization of 

 man against Asiatic cholera in the East and preventive inoculation practised by the 

 method of Haffkine appears to have given encouraging results. This method consists 

 in the subcutaneous injection of cultures of the cholera bacillus; first, those whose viru- 

 lence has been diminished, and then, those in which the virulence lias been exalted by 

 artificial means. 



Pfeiffer has shown that the spirillum of Asiatic cholera, put into the peritoneal 

 cavity of an artificially immunized guinea-pig, is quickly immobilized, swells, and be- 

 comes granular and soon disappears. A similar effect can be secured in tubes by a 

 mixture of the antitoxic serum and fresh serum to which the spirilla are added. This 

 lytic effect of the antitoxic serum upon the bacteria has been proposed as a test, on the 

 one hand, of the specific character of a suspected spirillum; and, on the other, with a 

 definitely known spirillum to employ the lytic action of the serum in a suspected case 

 of disease as a diagnostic test. 



1 For summary of characters of the cholera organism, methods of diagnosis, etc.. see 

 Kolle, in Kolleand WassermannVIIandbuch der Mikroorganismen," Bd. iii., S. i., 1903. 



