VIRULENT DISEASES. 205 



But to return to our septic vibrios. If air de- 

 stroys them, if their culture is impossible in contact 

 with air, how can septicaemia exist, since air is every- 

 where present ? How can blood exposed to the air 

 become septic from particles of dust on the sur- 

 face of objects or which the air holds in suspension? 

 Where can the septic germs be formed ? The objec- 

 tion seems a serious one, but it disappears before a 

 very simple experiment. Take some serum from 

 the abdomen of a guinea-pig which has died of acute 

 septicaemia. It will be found full of septic vibrios 

 in process of generation by fission. Let this liquid 

 be then exposed to the contact of air, with the pre- 

 caution of giving a certain depth to the liquid say, 

 a centimeter of depth. In some hours, if examined 

 with the microscope, the following curious spectacle 

 will be witnessed : In the upper layers the oxygen of 

 the air is absorbed, which is manifested by the already 

 changed colour of the liquid. There the filamentous 

 vibrio dies, and disappears under the form of fine 

 amorphous granulations deprived of virulence. At the 

 bottom of this layer of one centimeter in thickness, on 

 the contrary, the vibrios, protected from the approach 

 of oxygen by those of their own kind which have 

 perished above them, continue to multiply by fission 

 until by degrees they pass into the state of spores ; so 

 that instead of moving threads of all dimensions, the 

 length of which sometimes even extends beyond the 



