50 BIOLOGY OF PNEUMOCOCCUS 



with pneumococci. Incubated continuously at 37.5°, the pneumo- 

 cocci survived for four months. Truche and Cotoni 1422 added two 

 volumes of 15 per cent gelatin in physiological salt solution to 

 cultures grown at 37.5° in the "T" medium, sealed the tubes, and 

 kept them in the ice-box. In this way viable stock cultures could be 

 maintained for at least six months. Ungermann 5435 cultivated pneu- 

 mococci in concentrated rabbit serum and then protected the cul- 

 tures with a layer of sterile paraffin oil, with incubation at 37.5°. 

 Later, Truche 1421 modified Ungermann's method by first growing 

 strains on blood or serum agar, and then covering the surface 

 with formalinized serum. Preservation continued for a year, yield- 

 ing virulent material for inoculation. In a semi-fluid medium con- 

 sisting of one part of nutrient agar and five parts of sterile ascitic 

 or pleuritic fluids, with short incubation and storage at 8° to 10°, 

 Wadsworth (1903) 1454 preserved cultures in a viable condition for 

 three or more months. In these exudates without agar, the period 

 of viability was even greater. A similar medium with the addition 

 of glucose was described in 1930 by Velicanoff and Mikhailova. 1450 



Dehydration is an excellent physical method for the preserva- 

 tion of cultures of Pneumococcus, particularly in those cases in 

 which experiments continued over a long period of time require 

 that the characters of the strain be held uniform and constant. 

 Nissen (1891) 1013 first applied this principle to the drying of ster- 

 ile silk threads saturated with broth and serum-broth cultures, but 

 the results were only indicative of the success which was to attend 

 Heim's 631 efforts fourteen years later. Similar threads, soaked in 

 the blood of a cat dying of pneumococcal septicemia and dried 

 over calcium chloride in a desiccator, fourteen and sixteen months 

 later yielded in broth a growth of pneumococci possessing a viru- 

 lence equal to that of the original material. 



In the year of Nissen's publication, Bordoni-Uffreduzzi, 142 not 

 seeking a method of preservation, reported that pneumonic sputum 

 when dried on linen rags gave growth after twelve days' exposure 

 to direct sunlight, and as late as after fifty-five days of exposure 



