1893.] Bacteriology in its General Relations. 1053 
points suffice to show the influence that the study of the bacte- 
ria has exerted upon the technique of other lines of biological 
thought. 
Has it been able to any extent to aid in the solution of any 
of the general questions that have from time to time engaged 
the attention of all students of living phenomena? In con- 
sidering this, reference will be made mainly to those lines that 
are of special importance in the theoretical problems of biol- 
ogy. As has been previously stated, the main results of bac- 
teriology as yet are found in applied science, but the germ 
theories of fermentation, of nitrification, of sewage filtration, 
of nitrogen fixation, of the etiology of contagious diseases and 
of inflammation are monumental witnesses of the value of this 
department in the realm of pure science. 
Bacterial methods in the hands of the illustrious Pasteur 
were the means of combatting and effectually routing the 
heterogenists from their defence and proving beyond the sha- 
dow of a doubt, the accuracy and universality of the Harveian 
motto “ Omne vivum ex vivo.” 
Since the discovery of the laws, which are the foundational 
basis of the doctrine of evolution, every department of natural 
science has paid tribute to it, adding fact upon fact, and 
broadening the basis of the principles, formulated by the 
observant Darwin. Morphology and physiology in both 
branches of biology, as well as pathology, have furnished their 
quota of proof in this grand advance step in knowledge. 
Has bacteriology contributed its contingent to the general 
result on this and other vital problems? Does the testimony 
of the infinitely little corroborate that of the higher and more 
complex forms of life? 
The advantages of this group as types for study on many 
questions of this nature, have not as yet been generally appre- 
ciated. The practical side of the subject has naturally pre- 
sented the most attractive phase, and even the systematists 
have found but scant encouragement for their labors, except 
for the utilitarian purpose of species determination. 
The number of observers who have made this group of organ- 
isms a subject of special study with reference to general biologi- 
