TEXT-BOOK OF BACTERIOLOGY. 307 



can only be prepared by observing special measures of precaution. 

 By taking a 15^ gelatin and not allowing the temperature to rise 

 much above 24°, C, the gelatin will remain firm and colonies will be 

 developed. They appear under the microscope as small, roundish, 

 sharply-defined, slightly-granulated, whitish heaps, growing but 

 slowly, not passing beyond a moderate size, and never liquefying 

 the gelatin. 



On agar plates there are developed on the second day at breed- 

 ing heat delicate, shining, almost transparent, exceedingly small 

 drops, scarcely perceptible by the naked eye. 



Puncture culture in gelatin (15^ at 24° C.) after a short time as- 

 sumes a very characteristic appearance. Along the entire line of 

 inoculation large quantities of small white granules arise, distinctly 

 separated and resembling the picture of the streptococci of erysip- 

 elas. 



On oblique agar and blood-serum, a veil-like, transparent film 

 is developed, apparently composed of "single dew-drops." The 

 bacteria flourish in bouillon without perceptibly clouding it; only 

 a slight mist in older tubes betrays the presence of the micro- 

 organisms. 



The continuity of cultures on our artificial media is exceedingly 

 restricted. On agar-agar, for instance, the diplococcus usually dies 

 after four or five days and is no longer capable of development on 

 transmission to fresh media. It cannot hold out much longer on 

 gelatin; we may obtain somewhat older cultures only in bouillon. 



Susceptible animals (mice. Guinea-pigs, and rabbits being among 

 them, according to Frankel's investigations) infected by this 

 micro-organism usually perish after twenty-four to fortj'-eight 

 hours. It does not matter how the material is obtained ; it maj' be 

 taken directly from the lung tissue, whenever microscopic examin- 

 ation has established the presence of bacteria, better still the agar 

 plates prepared with tissue-fluid may be used, or cultures in gelatin 

 or agar-agar. Young bouillon-cultures are best adapted, of which 

 0.1 to 0.3 c.cm. is used. 



The first symptoms of the disease are perceived soon after in- 

 jection under the rabbit's dorsal or abdominal skin. The animal 

 does not eat, sits sadly in a corner of its cage, its temperature is 

 clearly increased, and death ensues almost without exception after 

 from twenty-four to forty-eight hours. Post-mortems furnished 

 under all circumstances the same characteristic picture. Very 

 slight if any reaction at the inoculation spot; much swelling of the 

 spleen (frequently increased to twice its ordinary size) which is at 

 the same time hard and reddish- brown; large quantities of bacilli. 



