TKANSIENT MODIFICATIONS 109 



alterations in the medium of growth. Take, for instance, the 

 Eberth-Gaffky bacillus of enteric fever. This is a bacillus of 

 fair size — three to five times as long as it is broad, with rounded 

 ends, and, thanks to the possession of long vibratile cilia along 

 its sides, it is normally endowed with great rapidity of motion. 

 It has, further, the property of resisting the action of fairly large 

 amounts of carbolic acid in the medium of growth — a property 

 which has been utilized by Vincent to separate it out from other 

 microbes, and to gain pure diagnostic cultures from the faeces 

 of those affected by the disease, or from contaminated water. 

 If beef-broth be taken containing about 1 part of carbolic acid 

 in 600, the Eberth - Gaff ky bacillus, almost alone among the 

 bacteria, will grow in it at a temperature of 42° C, rendering 

 the broth turbid in the course of a few hours. But if a drop of 

 this be examined, one finds not the characteristic motile bacillus, 

 but shorter forms and often diplococci, and these are non-motile. 

 In fact, there is an absolute want of resemblance to the type 

 bacillus. Yet if a culture of these be made in the ordinary beef- 

 broth of the laboratory, devoid of carbolic acid, there is an 

 almost immediate return to type. 1 But there is a much simpler 

 method of gaining polymorphism in connexion with this microbe. 

 Employing a series of potatoes of diverse origin, it is found that 

 upon some the growths of the microbe are atypical not only in 

 naked-eye appearance but also under the microscope, developing 

 into long filaments. This atypical growth has been commented 

 upon by numerous observers, including Frankel and Simmonds, 2 

 Buchner, 3 Schiller, 4 and Kamen. 5 Buchner's observations 

 render it probable that this atypical growth is in close relation- 

 ship to the known varying acidity of the potato. 



Still more striking are the results obtained by Charrin 6 in the 

 case of the small bacillus of blue pus, which within the body 

 of an infected animal, or grown in beef-broth, is what may be 

 termed a microbacillus — a minute short bacillus, the individuals 

 being often attached in pairs end to end. 



If /3-naphthol be added to the beef-broth in the proportion 



1 Vincent, Comptes rendus de la Soc. de Biologie, 1890, No. 5. 



2 Frankel and Simmonds, Zeitschrift f. Hygiene, ii., 1887, p. 138 



3 Buchner, Centralblatt f. Bakteriologie, iv., 1888, p. 353. 



4 Schiller, Arbeiten aus dem kais. Gesundheitsamt, v. 



5 Vide Petruschky, Centralblatt f. Bakteriologie, vi., 1889, p. 657 



6 Charrin, La Maladie pyocyanique, Paris, Steinheil, 1889. 



