124 



Lectures on Bacteria. 



[I xii. 



f 



2 



disputed points on the present occasion, leaving them to be 

 examined in the special literature of the subject (56), and con- 

 fine ourselves to cases which have been 

 certainly ascertained, especially those in 

 mammals. Susceptibility to infection varies 

 with the species, as appears from what 

 has been already said ; within the limits 

 of the species it varies according to race 

 and age, and with the individual. 



Anthrax is a widely-spread form of 

 disease; at the same time it is matter of 

 long experience, that it appears with un- 

 usual frequency in certain districts, and 

 that these anthrax-districts are especially 

 dangerous to herds of cattle, and are there- 

 fore dreaded by breeders. 



The clinical aspect of the disease is 

 different in different species of animals ; 

 in larger ones it is said to run a com- 

 paratively slow course, being accompanied 

 with violent fever, &c., and in most cases 

 but not always ends in death. Mice and 

 guinea-pigs succumbed to the disease 

 almost without exception in the cases ob- 

 served, but without showing any particularly striking symptoms 



Fig. 1 8. 



Fig. 1 8. A Bacillus Anthracis. Two filaments partly in an advanced stage 

 of spore-formation ; above them two ripe spores escaped from the cells. From 

 a culture on a microscope-slide in a solution of meat-extract. The spores 

 are drawn a little too narrow ; they are nearly as broad as the breadth of 

 the mother-cell. B Bacillus subtilis. 1 fragments of filaments with ripe 

 spores. 2 commencement of germination of spore ; the outer wall torn trans- 

 versely. 3 young rod projecting from the spore in the usual transverse 

 position. 4 germ-rods bent into the shape of a horse-shoe, one subsequently 

 with one extremity released. 5 germ-rods already grown to a considerable 

 size, but with both extremities still fixed in the spore membrane. All 

 magn. 600 times. 



