346 Tue MIcROSCOPE. 
that their deleterious work is usually done, not by their pres- 
ence but by their poisonous excretions, detracts nothing from 
the interest. Dr Prudden’s description of the struggle be- 
tween the poisonous bacteria and the white blood-cells is dra- 
matic. When these bacteria get into the tissues they may begin 
to grow, producing a small amount of the poison called a pto- 
maine, about which poisoned point the white blood-cells gather 
just as they would about a wound. The arrival of these cells 
upon the scene signalizes the commencement of a life-and-death 
_ struggle between the bacteria and the cells. The latter attempt 
either to swallow and thus kill and digest the bacteria, or so 
closely to surround them as to cut off their oxygen and food 
supply, and so destroy them. The bacteria on the other hand, 
so long as they can grow and proliferate, produce their poison, 
which may kill the white blood-cells and break up the tissues 
round about. It is the story of the two knights in the arena, 
with much more important results to the waiting creature in 
whose body they are contending, and whose fate depends upon 
the strength and endurance of the microscopic combatants. 
The author tells in his agreeable way what- the bacteria are, 
many of the things that they do, and how they are studied by 
the experts. He describes some bacterial curiosities, among 
them luminous bacteria, the color-forming species, the mysteri- 
ous appearance of apparently bloody drops on the Host to the 
terror alike of priest and layman; he pictures the strife between 
the yeast cells and the bacteria in wine and beer making, with 
other interesting and important matters. A curious fact men- 
tioned is that among some of these minute plants there is a sort 
of one-sided Damon and Pythias relationship, for in the attempts 
to isolate certain forms by culture, it is found that occasionally 
two species can be grown together, but if an attempt be made to 
separate them, one of them will always die. The nature of this 
friendly tie is not known. 
The chapter on the bacteria of Tuberculosis, Typhoid Fever, 
Asiatic Cholera, and other mortal diseases contains the latest 
opinions and discoveries, while those on impure food, water and 
ice as the sources of bacterial diseases are valuable and sug- 
gestive. The little book is unique in bacteriological literature, 
and can be heartily commended to the readers of THE Micros- 
COPE as one in which they will not be disappointed. 
