420 BOTANICAL BIOLOGY. 



are ancillary to and aid digestion. But it is easy to see that other kinds 

 may be introduced, or those already present may be called into abnor- 

 mal activity, and fermentative processes maybe set up of a very incon- 

 venient kind. These may result in mere digestive disorder, or in the 

 production of some of those poisonous derivatives of proteids of which I 

 have spoken, the effect of which upon the organism may be most disas- 

 trous. 



The access of Bacteria to the blood is a far more serious matter. 

 They produce phenomena the obvious analogy of which to fermentative 

 processes has led to the resulting diseases being called zymotic. Take 

 for example, the disease known as " relapsing fever." This is contagious. 

 After a period of incubation, violent fever sets in, which lasts for some- 

 thing less than a week, is then followed by a period of absence, to be 

 again followed in succession by one or more similar attacks, which ulti- 

 mately cease. Kow you will observe that the analogy to a fermentative 

 process is very close. The period of incubation is the necessary inter- 

 val between the introduction of the germ and its vegetative multitjlica- 

 tion in sufficient numbers to appreciably affect the total volume of the 

 blood. The rise in temperature and the limited duration of the attack 

 are equally, as we have seen, characteristic of fermentative processes, 

 while the bodily exhaustion which always follows fever is the obvious 

 result of the dissipation by the lermeut organisms of nutritive matter 

 destined for the repair of tissue waste. During the presence of this 

 fever there is present in the blood an organism, Spirochwte obermeierl, 

 so named after its discoverer. This disappears when the fever subsides. 

 It is found that if other individuals are inoculated with blood taken 

 from patients during the fever attack, the disease is communicated, but 

 that this is not the case if the inoculation is made during the period of 

 freedom. The evidence then seems clear that this disease is due to a 

 definite organism. The interesting point however arises, why does 

 the fever recur, and why eventually cease ? The analogy of fermenta- 

 tion leads to the hypothesis that as in the uase of yeast the products of 

 its action inhibit after a time the further activity of the Sjiirochwte. The 

 inhibiting substance is no doubt eventually removed partially from the 

 blood by its normal processes of depuration, and the surviving individ- 

 uals of AS^^/roc/ta-fe can then continue their activity, as in lactic fermenta- 

 tion. With regard to the final cessation of the disease, there are facts 

 which may lead one to suppose that in this as in other cases sufficient of 

 the inhibiting substance ultimately remains in the organism to protect 

 it against any further outbreak of activity on the part of the Spiroehwte. 

 Here we have an example of a disease which, though having a well- 

 marked zymotic character, is comparatively harmless. In anthrax, 

 which is known to be due to Bacillus anthracis, we have one which is, 

 on the contrary, extremely fatal. I need not enter into the details. It 

 is sufficient to say tTiat there is reason to believe that the Bacillus pro- 

 duces, as one of those by-productsof protoplasmic destruction to which 

 I have alreadj^ alluded, a most virulent poison. But the remarkable 



