ETIOLOGY OF SPLENIC FEVER. 253 



grew accustomed to the idea that the stricken animals 

 might have contracted the germs of the malady from 

 the outer world, without any spontaneous birth, 

 strictly so called, of the disease. This opinion was 

 strengthened by a knowledge of the spores of the splenic 

 bacillus. Pasteur, aided by Messieurs Chamberland 

 and Roux, commenced experiments with a view to 

 solving this difficult etiological question. The first 

 experiments took place in the fields of a farm at the 

 village of St. Germain, near Chartres. Several groups 

 of sheep were fed on lucern grass which had been 

 sprinkled with artificially-reared splenic fever bacteria, 

 or with their germs or spores. Although all the sheep 

 of the same group absorbed an immense number of 

 the spores of the parasite, many survived, even after 

 being visibly affected. Those that died showed all the 

 symptoms of what is called spontaneous splenic fever. 

 The period of incubation lasted as long as eight or ten 

 days, although, in its latter stages, the disease exhibited 

 those startling features which have caused a belief 

 that the incubating period is a very short one short, 

 that is to say, for those conditions of contagion where 

 the parasite is not deposited in its pure state under 

 the animal's skin. 



But if prickly plants (notably the pointed ends of 

 dried thistle leaves, or beards of barley blades cut 

 into little bits about a centimeter in length) were 

 added to this infected food, the mortality increased to 



