222 LABORATORY EXERCISES IN BACTERIOLOGY. 



Some bacteria frequently, under comparatively normal circumstances, and many 

 forms under conditions of difficult life (as from unfavorable amount or quality of food, 

 moisture, atmosphere, temperature, etc.), may produce within their substance certain 

 highly refractive, definite bodies known as spores, which retain the vital power of the 

 bacteria under adverse states for a long period; and from which subsequently new 

 bacteria of the same type originate. They are thus analogous to the spores or seed 

 bodies of higher types of fungi, but are better thought of as really only resting forms 

 of the original bacterial bodies. They are of importance in the study of the different 

 varieties of bacteria for identification and appreciation of qualities of vital persistence. 



Such spores, while probably always truly 

 rip A within the bacterial body in their forma- 

 Q tion (hence endospores}, are sometimes 



seen free (exospores} in the midst of adult 



_ _ - *2*o* bacteria, or attached to the ends of the 



E f 9- bacterial cells (arthros pores'), the envelope 



of the original bacterial cell having dis- 

 FIG. 65.-TYPES OF SPORULATION. appeared from about the spore R . g a 



A,B, C, D, and ^Endospores. ^and G . fe . 



Exospores. A, B, D. Spores equatorial. 



Cand. Spores polar. F. Arthrospores. formed from one bacterium; from the 



position in which it occurs it is described 



as equatorial or polar (Fig. 65) ; and the cell outline is apt therefrom to be swollen 

 into claustridium or club shape. 



For the development of these spores into the ordinary vegetative forms there 

 must be afforded proper conditions of life, particularly plenty of moisture, through the 

 imbibition of which apparently the bacterium is enabled to grow and force its mass 

 through the capsule of the spore. This is spoken of as germination of the spore; it 

 may take place at one or both poles or along the sides, and is hence described as polar, 

 bipolar, or equatorial germination (Fig. 66). Usually spores are met among the rod- 

 shaped organisms, but the globular forms are now and again also capable of spore 



, 



lj 





FIG. 66. FORMS OF BACILLI SHOWING SPORES. 



formation. They are often easily seen in ordinarily stained preparations as rounded, 

 or oval bodies within, or among, or apparently on the ends of the ordinary bacteria, 

 unstained and peculiarly shining. Their refraction is especially appreciated when 

 the field is darkened by contraction of the diaphragm of the substage. By prolonged 

 staining with the application of considerable heat and the use of a mordant. in the 

 staining fluid, they may be colored; after which they are usually with more difficulty 

 decolorized than the ordinary bacteria, which makes possible their differentiation. 

 The following method has been found very satisfactory for their demonstration (modi- 

 fied from Hauser 1 ) : A drop of water is placed on a slide and in it diffused a small 

 amount of a sporulating culture of some organism. The drop is spread and nearly 



