8 MEDICAL BACTERIOLOGY 



square ends, long slender bacilli, some with round, others with square ends, 

 short slender and short plump bacilli, some having round and others square 

 ends; bacilli capable of locomotion and others that are not. Some species of 

 bacilli, but not all, have the faculty of producing spores (endospores). 



SPIRILLA 



Spirilla show marked variations in size just as bacilli do. They may be 

 divided into three groups: 



1. Rigid nonmotile spirals (spirosoma). 



2. Rigid motile spirals (spirillum). 



3. Flexible, motile spirals (spirochaeta). 



Spirilla propagate by cell division, cleavage being in some instances longi- 

 tudinal as well as transverse. Spore formation is unknown. 



The family and genus characteristics of bacteria are permanent so far as 

 is known. Each species is a distinct entity; staphylococci never become 

 gonococci, colon bacilli never become anthrax bacilli, tubercle bacilli are al- 

 ways tubercle bacilli, they never produce anything but tubercle bacilli; muta- 

 tion from one form to another has not been proved. 



Spontaneous development of bacteria does not occur; all bacteria origi- 

 nate from bacteria. There is no other form of development. 



The term bacteria is used to designate rod-shaped schizomycetes, it is also 

 used when referring to the entire group of schizomycetes, and in its broadest 

 sense includes other higher groups of organisms conveniently classified as 

 "higher forms of bacteria." 



The higher bacteria embrace the actinomyces, caldothrices, leptothrices, 

 blastomycetes and hyphomycetes (see page 135). 



Bacteria may be differentiated and classified according to their physiology, 

 some species otherwise indistinguishable have peculiar secretions and others are 

 distinguished by the physical and chemical changes they produce in the medium 

 upon which they grow. 



For those whose work frequently necessitates the identification of bacteria 

 of soil, water and foodstuffs, "A Manual of Determinative Bacteriology" 

 by F. D. Chester (The Ma,cmillan Co., New York) is a most valuable aid. 



It is highly important that as soon as possible we can arrive at the use of a 

 proper and uniform nomenclature for bacteria. At the present time, unfor- 

 tunately, such is not in use. Advanced students are earnestly recommended 

 to consider this subject and to read especially " Vuillemin Genera Schizomy- 

 cetum, Annales Mycologici, xi, 512-527." Also Buchanan, R. E., Journal of 

 Bacteriology, vol. i, No. 6, pp. 591-596, November, 1916. 



