ii6 Lectures on Bacteria. [? xi. 



as a regular, if not in most cases an absolutely indispensable 

 thoroughfare, since when introduced with the food they find a 

 home and nourishment in it for the first stages of their develop- 

 ment, and then complete it on the voided faeces. This is shown 

 by the abundant and remarkable Fungus-flora of dung. 



It is known that many forms of Bacteria occur in large 

 numbers in the contents of the intestinal canal. A more 

 thorough sifting and sorting of most of the species has yet to be 

 undertaken. In the human intestine Nothnagel has distinguished 

 Bacillus subtilis, B. Amylobacter, and other not clearly defined 

 forms, and Bienstock (50) his drum-stick Bacillus. Kurth found 

 his Bacterium Zopfii in the intestine of fowls (see page 22). To 

 these examples must be added the constant, and according to 

 van Tieghem (see page 102), the essential presence of Bacillus 

 Amylobacter in the stomachs of ruminants (52). 



The acid of the gastric juice may prevent the appearance of 

 most of the Bacteria in the normal contents of the stomach (in 

 the rennet-stomach in ruminants). Koch's researches into 

 anthrax, to be noticed again presently, have even shown that 

 Bacillus Anthracis in the vegetative states is killed by the gastric 

 juice, and only its spores maintain their vitality. This may be 

 the case with some other species, and it may be of some import- 

 ance that a kind of sorting thus takes place in the normal 

 stomach, by means of which some only of the Bacteria intro- 

 duced with the food reach the intestinal canal in the living state. 



That the gastric juice has not always an injurious effect, but 

 that here too there is a difierence between one case and another, 

 is shown by the researches of Miller and W. de Bary (52). We 

 are acquainted with one species, the well-known Sarcina ven- 

 triculi (Fig. 14), which thrives particularly well in the human 

 stomach. This species forms packets in the shape of almost 

 perfect cubes of roundish cells arranged in regular layers 

 parallel with the surfaces of the cube, and kept firmly united by 

 tough gelatinous membranes. Comparison shows plainly that 

 the packets are formed in the manner which can be directly 



