1889.] MICROSCOPICAL JOURNAL. 5 



The Character of Bacteria.* 



By B. M. BOLTON, M. D., 



PROFESSOR OF PHYSIOLOGY, HYGIENF. AND BACTERIOLOGY IN THE UNIVERSITY OF SOUTH CAROLINA . 



A great many phenomena which occur around us every day are due 

 to the activity of microscopic beings. The subject has aroused very 

 great interest, not only among strictly scientific men, but in persons 

 engaged in other callings as well ; for it has been shown that many of 

 the most important processes in natm - e are caused bv bacteria. The sub- 

 jects which are of most interest to us at present are the decomposition 

 of vegetable and animal matter, and infectious diseases. Strictly speak- 

 ing, fermentation is not due to bacteria. 



Bacteria are very minute plants. They are the smallest living things 

 that we know. Many millions of them together do not weigh as much 

 as a grain of sand. The individual bacterium can only be seen with a 

 microscope of high power. But most of them grow so rapidly that 

 even starting from an invisible amount, they form a mass readily observ- 

 able with the naked eye in a few days. They form, for the most part, 

 very characteristic masses upon potatoes or nutrient gelatine, so that, 

 even without the microscope, we see marked differences. Their cul- 

 tures are of various colors, and they differ also in other respects. So 

 we can study bacteria at the present day largely without the microscope. 



There are other minute plants which also cause diseases. Certain 

 mould fungi belonging to the same class as the mould every one has 

 seen upon old bread and cheese also cause disease, but bacteria cause 

 such diseases as typhoid fever, cholera, anthrax, etc., and so they are 

 of more interest at present. 



Fermentation is caused by the yeast fungi, which are larger than 

 bacteria, and are ovoid in shape. They multiply by budding. A little 

 knob appears on one side of one of the oval bodies and grows and sends 

 out another knob or bud. The bacteria multiply by fission. A bac- 

 terium divides into two, which again divide, etc. Bacteria are divided 

 into (i) cocci or round bacteria, (2) bacilli or rod-shaped bacteria, and 

 (3) spirilla or cork-screw shaped bacteria. But how are we able to 

 assert so confidently at the present day that decomposition and disease 

 are caused by bacteria? The proof is perfectly conclusive. Take a 

 piece of meat, or vegetables, or fruits of any sort, and free them from 

 bacteria, and then prevent the access of bacteria afterwards ; the sub- 

 stances so treated do not spoil. Cut out a piece of flesh from a freshly 

 killed animal and merely stop it up in a tube plugged with raw cotton, 

 and if you succeed in doing this without getting any bacteria on it, it 

 can be preserved indefinitely. Or take a fresh piece of flesh or other 

 perishable article, and stop it up in this way, and then kill out the bac- 

 teria by heat. Articles treated in this way are also prevented from 

 spoiling. It is not necessary to exclude the air, for of course the raw 

 cotton does not exclude it. All that the cotton does is to filter out the 

 bacteria, so that the air which comes in contact with the substance to 

 be preserved is purified from the things which cause decomposition. 

 In every case where there is decomposition there are always bacteria^' 

 and where thei - e is no decomposition there are no bacteria. 



The proof in the case of certain infectious diseases of animals and 



*From a report of the Department of Agriculture of South Carolina, October, 1S88. 



