4$ 2 THIRD PART.- -BACTERIA OR SCHIZOMYCETES. 



R. Hartig has already drawn attention. One reason for this may he that the parts 

 of plants have usually an acid reaction. At the same time Wakker 1 has recently 

 described a disease in the hyacinth known in Holland as the yellow sickness, 

 the characteristic symptom of which is the presence of yellow slimy masses of Bacteria 

 in the vessels. In the resting (autumnal) bulb the masses of Bacteria are confined 

 to the vascular bundles of the bulb-scales; at flowering time they are found also in the 

 leaves, and not in the \< -sels only but in the parenchyma also, where they fill the 

 intercellular spaces, destroy the cells, and ultimately emerge through the ruptured 

 epidermis and appear on the outside. The case demands a thorough investigation. 



The Bacteria on the other hand which are parasitic in living animals are, 

 according at least to prevailing views, comparatively numerous, and the most 

 prominent feature in them is their facultative parasitism. Of this we have instances 

 which have been investigated with some care and may be considered as well 

 established, and it will be well to give here a special account of one of the most 

 important of the number, namely Bacillus Anthracis. 



The structure and development of this species have been already portrayed in 

 Fig. 195. It attacks the Mammalia, especially rodents and ruminants, with the 

 exception of some species and individuals ; mice, guinea-pigs, rabbits, sheep and 

 cattle are unequally liable to be infected by it in the descending order. It will also 

 attack human beings. It is communicated with difficulty to dogs, more readily to 

 cats. Observers are not agreed as to the degree of liability of birds, frogs and fishes 

 to be infected with it, and we cannot further discuss their statements in this place. 

 We know from Rayer, Pollender and Davaine that it causes the disease known as 

 anthrax in the animals first mentioned. My own experiments on which this account 

 is partly based were chiefly made on guinea-pigs, and on material obtained from 

 them. 



When the Bacillus has gained admission into the blood of an animal capable of the 

 infection, it grows and multiplies in the rod-form described above to such a degree 

 that the entire mass of the blood is permeated by these organisms. The animal 

 sickens as the Bacillus multiplies and the result is usually fatal. The Bacillus may 

 find its way into the blood directly by intentional introduction of rods or spores or 

 from accidental wounds ; a prick of a needle charged with rods or spores, so slight 

 as not to draw blood, is sufficient to give the infection to a sensitive animal. But it 

 may also reach the blood from the intestinal canal, into which it is conveyed in the 

 natural way only, that is through the mouth with the food. Rods introduced in this 

 way have no further effects, if the digestive passages are without a wound ; tin y 

 probably perish in the acid contents of the stomach. But if spores are introduced the 

 animal takes the infection. The spores pass unharmed through the acid stomach 

 and germinate in the alkaline contents of the intestinal canal, and the rods which are 

 the product of germination are found in the mucous membrane of the canal, having 

 forced their way probably through the lymph-follicles and Beyer's patches, as Koch 

 supposes. From hence the way is open through the capillaries into the blood- 

 passages. 



According to Koch's investigations the infection comes much more frequently 



1 Bot. C'cntralblatt, 14. p. 315. 



